it is...for sb. to do...和it is...of sb. to do...的用法 it is +adj+for sb to do sth与it...

It is +of sb. to do sth \u4e0e It is +for sb. to do sth\u6709\u4f55\u533a\u522b \u8be6\u7ec6\u5177\u4f53

\u82e5\u5f62\u5bb9\u8bcd\u662f\u63cf\u8ff0\u4e0d\u5b9a\u5f0f\u884c\u4e3a\u8005\u7684\u6027\u683c\u3001\u54c1\u8d28\u7684\uff0c\u5982kind\uff0cgood\uff0cnice\uff0cright\uff0cwrong\uff0cclever\uff0ccareless\uff0cpolite\uff0cfoolish\u7b49\uff0c\u7528of sb.\u3002 It\u2019s very kind of you to help me. \u4f60\u80fd\u5e2e\u6211\uff0c\u771f\u597d\u3002 It\u2019s clever of you to work out the maths problem. \u4f60\u771f\u806a\u660e\uff0c\u89e3\u51fa\u4e86\u8fd9\u9053\u6570\u5b66\u9898\u3002 \u82e5\u5f62\u5bb9\u8bcd\u4ec5\u4ec5\u662f\u63cf\u8ff0\u4e8b\u7269\uff0c\u4e0d\u662f\u5bf9\u4e0d\u5b9a\u5f0f\u884c\u4e3a\u8005\u7684\u54c1\u683c\u8fdb\u884c\u8bc4\u4ef7\uff0c\u7528for sb.\uff0c\u8fd9\u7c7b\u5f62\u5bb9\u8bcd\u6709difficult\uff0ceasy\uff0chard\uff0cimportant\uff0cdangerous\uff0c\uff08im\uff09possible\u7b49\u3002 It\u2019s very dangerous for children to cross the busy street. \u5bf9\u5b69\u5b50\u4eec\u6765\u8bf4\uff0c\u7a7f\u8fc7\u7e41\u5fd9\u7684\u8857\u9053\u5f88\u5371\u9669\u3002 It\u2019s difficult for us to finish the work. \u5bf9\u6211\u4eec\u6765\u8bf4\uff0c\u5b8c\u6210\u8fd9\u9879\u5de5\u4f5c\u5f88\u56f0\u96be\u3002 \u6ce8\u610f\u25cb \u25cb\u25cb\u25cb\u25cb\u25cb\u25cb\u25cb\u25cb\u25cb\u25cb\u25cb of sb. \u7684\u53e5\u578b\u901a\u5e38\u90fd\u53ef\u8f6c\u6362\u4e3a\u4e0d\u5b9a\u5f0f\u4f5c\u72b6\u8bed\u7684\u53e5\u5b50\uff0c\u4f46for sb. \u53e5\u578b\u4e0d\u53ef\u4ee5\u3002 It\u2019s very nice of you to offer me a seat. = You are nice to offer me a seat. \u5341\u5206\u611f\u8c22\u4f60\u7ed9\u6211\u8ba9\u5ea7\u3002 It is careless of him to lose so many things. = He is careless to lose so many things. \u4ed6\u4e22\u4e86\u8fd9\u4e48\u591a\u4e1c\u897f\uff0c\u771f\u662f\u592a\u7c97\u5fc3\u4e86\u3002 It\u2019s very important for you to practise your oral English in daily life. \u5728\u65e5\u5e38\u751f\u6d3b\u4e2d\u7ec3\u4e60\u4f60\u7684\u82f1\u8bed\u53e3\u8bed\u975e\u5e38\u91cd\u8981\u7684\u3002 \u8fd9\u53e5\u8bdd\u4e0d\u80fd\u8bf4\u6210\uff1aIt is very important of you to practise\u2026

\u7528for \u662f\u56e0\u4e3a\u524d\u9762\u7684adj\u662f\u6765\u63cf\u8ff0do\u540e\u9762\u7684sth.
\u7528of \u7684\u8bdd,adj\u5c31\u7528\u6765\u5f62\u5bb9sb\u7684
it is adj of sb to do,\u8fd9\u91cc\u7684\u5f62\u5bb9\u8bcd\u662f\u5f62\u5bb9\u4eba\u7684\u6027\u683c\u7279\u5f81\u7684,\u5982nice,kind clever,foolish,smart,\u90fd\u662f\u5f62\u5bb9\u4eba\u7684,
it is adj for sb to do\u5c31\u662f\u666e\u901a\u7684\u5f62\u5bb9\u8bcd,\u5982hard,impossible,important
\u7ffb\u8bd1\uff1a\u5bf9\u6211\u4eec\u6765\u8bf4\u5b66\u4e60\u82f1\u8bed\u592a\u96be\u4e86

it is+adj+for sb to do...
it is+adj+of sb to do ....\u7684\u542b\u4e49\u53ca\u533a\u522b
\u4e00.\u5bfc\u5165
It is kind of you to help me.\u4f60\u80fd\u5e2e\u6211\u592a\u597d\u4e86.\uff08kind \u5f62\u5bb9\u7684\u662fyou\uff09
It is beneficial for you to do sports.\u8fd0\u52a8\u5bf9\u4f60\u6709\u76ca.\uff08beneficial\u5f62\u5bb9\u7684\u662fdo sports\uff09
\u4e8c.\u8868\u8fbe\u542b\u4e49:
1.it is+adj+for sb. \u5c31\u662f\u201c\u505a\u2026\u5bf9\u67d0\u4eba(for sb)\u6765\u8bf4\u600e\u4e48\u6837(adj)\u201d
2.it is+adj+of sb. \u5c31\u662f\u201c\u67d0\u4eba\u505a\u2026(of sb)\u600e\u4e48\u6837(adj)\u201d
\u4e09.\u8fa8\u6790:it is+adj+for sb\u548cit is+adj+of sb.
\u2460\u201cIt\u2019s +adj.+of+sb.+\u4e0d\u5b9a\u5f0f\u201d\u8868\u793a\u201c\u67d0\u4eba(\u505a\u67d0\u4e8b)\u600e\u4e48\u6837\u201d \u4e00\u822c\u7528\u8868\u793a\u4eba\u7269\u7684\u6027\u683c,\u54c1\u5fb7.\u8868\u793a\u4e3b\u89c2\u611f\u60c5\u6216\u6001\u5ea6\u7684\u5f62\u5bb9\u8bcd.\u82e5\u5f62\u5bb9\u8bcd\u662f\u63cf\u8ff0\u903b\u8f91\u4e3b\u8bed(\u884c\u4e3a\u8005\u5373of\u540e\u7684sb)\u7684\u6027\u683c\u3001\u54c1\u8d28\u7279\u5f81\u7684\u5f62\u5bb9\u8bcd. \u8fd9\u4e2aadj.\u662f\u7528\u6765\u5f62\u5bb9sb.\u7684.
of\u540e\u7684\u5bbe\u8bed\u80fd\u4e0e\u524d\u9762\u7684\u5f62\u5bb9\u8bcd\u6784\u6210\u4e3b\u8868\u5173\u7cfb. \u8fd9\u7c7b\u5f62\u5bb9\u8bcd\u6709:
good(\u597d\u7684),kind(\u53cb\u5584\u7684),
nice(\u53cb\u597d\u7684),polite(\u6709\u793c\u8c8c\u7684),
clever(\u806a\u660e\u7684),foolish(\u611a\u8822\u7684),
lazy(\u61d2\u60f0\u7684), right(\u6b63\u76f4\u7684)
careful(\u7ec6\u5fc3\u7684),careless(\u7c97\u5fc3\u7684),
right(\u6b63\u786e\u7684),wrong(\u9519\u8bef\u7684)
wise, clever, nice, kind, silly,
rude, wrong, right, foolish,
natural, stupid, bad, brave,
cruel, honest,naughty,wise,rude\u7b49.\u4f8b\u5982:
It\u2019s very kind of you to help me.(=You are very kind to help me.)\u4f60\u80fd\u5e2e\u52a9\u6211,\u771f\u597d.
It's very kind of you to look after my cat.\u4f60\u80fd\u7167\u770b\u6211\u7684\u732b,\u771f\u597d.
It\u2019s kind of you to say so.(=You are kind to say so)
It\u2019s very rude of her to say such words.(=She is very rude to say such words.)\u5979\u8bf4\u8fd9\u6837\u7684\u8bdd,\u771f\u7c97\u9c81.
It\u2019s foolish of him to go alone.(=He is foolish to go alone.)\u4ed6\u5355\u72ec\u51fa\u53bb\u592a\u50bb\u4e86.
It's very nice of you to help me. \u4f60\u6765\u5e2e\u52a9\u6211,\u4f60\u771f\u662f\u592a\u597d\u4e86.
It\u2019s clever of you to work out the maths problem. It's very kind of you to look after my cat.
\u4f60\u771f\u806a\u660e,\u89e3\u51fa\u4e86\u8fd9\u9053\u6570\u5b66\u9898.
It\u2019s foolish of you to do that.
It\u2019s wrong of the other children to make fun of you.
\u2461\u201cIt\u2019s+adj.+for+sb.+\u4e0d\u5b9a\u5f0f\u201d\u8868\u793a\u201c\u505a\u67d0\u4e8b\u5bf9\u67d0\u4eba\u6765\u8bf4\u600e\u4e48\u6837\u201d.\u5e38\u7528\u4e8e\u8868\u793a\u4e8b\u7269\u7684\u7279\u5f81\u7279\u70b9,\u8868\u793a\u5ba2\u89c2\u5f62\u5f0f\u7684\u5f62\u5bb9\u8bcd.\u82e5\u5f62\u5bb9\u8bcd\u662f\u63cf\u8ff0\u505a\u7684\u4e8b\u60c5\uff08\u5373adj\u63cf\u8ff0\u7684\u662fto do\uff09,\u4e0d\u662f\u5bf9\u4e0d\u5b9a\u5f0f\u884c\u4e3a\u8005\u7684\u54c1\u683c\u8fdb\u884c\u8bc4\u4ef7,\u7528for sb.\u8fd9\u7c7b\u5f62\u5bb9\u8bcd\u6709:
important(\u91cd\u8981\u7684),necessary(\u5fc5\u8981\u7684),
difficult(\u56f0\u96be\u7684),easy(\u5bb9\u6613\u7684),
hard(\u8270\u96be\u7684),dangerous(\u5371\u9669\u7684),
safe(\u5b89\u5168\u7684),useful(\u6709\u76ca\u7684),
pleasant(\u8212\u9002\u7684),interesting(\u6709\u8da3\u7684),
impossible(\u4e0d\u53ef\u80fd\u7684),
right(\u6b63\u786e\u7684) likely(\u53ef\u80fd\u7684)\u7b49\uff0c\u4f8b\u5982:
It\u2019s not easy for them to learn a foreign language.(=To learn a foreign language is not easy for them.)
\u5bf9\u4e8e\u4ed6\u4eec\u6765\u8bf4\u5b66\u597d\u4e00\u95e8\u5916\u8bed\u4e0d\u5bb9\u6613.
It's very hard for him to study two languages(=To study two languages is very hard for him).
\u5bf9\u4ed6\u6765\u8bf4\u5b66\u4e24\u95e8\u5916\u8bed\u662f\u5f88\u96be\u7684.
It\u2019s very important for students to listen to teachers carefully.(=To listen to teachers carefully is very important for students.)\u5bf9\u4e8e\u5b66\u751f\u6765\u8bf4\u4e0a\u8bfe\u8ba4\u771f\u542c\u8001\u5e08\u8bb2\u8bfe\u662f\u975e\u5e38\u91cd\u8981\u7684.
It\u2019s necessary for us to get to school on time.(=To get to school on time is necessary for us.)
\u5bf9\u4e8e\u6211\u4eec\u6765\u8bf4\u6309\u65f6\u5230\u6821\u662f\u975e\u5e38\u5fc5\u8981\u7684.
It\u2019s important for her to come to the party.=It is important that she should come to the party.
\u5bf9\u5979\u6765\u8bf4\u6765\u53c2\u52a0\u805a\u4f1a\u5f88\u91cd\u8981.
It\u2019s very dangerous for children to cross the busy street.\u5bf9\u5b69\u5b50\u4eec\u6765\u8bf4,\u7a7f\u8fc7\u7e41\u5fd9\u7684\u8857\u9053\u5f88\u5371\u9669.
It\u2019s difficult for us to finish the work. \u5bf9\u6211\u4eec\u6765\u8bf4,\u5b8c\u6210\u8fd9\u9879\u5de5\u4f5c\u5f88\u56f0\u96be.
\u2462\u6ce8\u610f:for \u4e0eof \u7684\u8fa8\u522b\u65b9\u6cd5:
I.\u533a\u522b:
1.\u542b\u4e49\u4e0a\u7684\u533a\u522b:
\u4e24\u79cd\u53e5\u578b\u7684\u4e3b\u8c13\u5173\u7cfb\u4e0d\u4e00\u6837.
It is+adj+for sb to do. adj\u5e94\u8be5\u662f\u5bf9\u505a\u8fd9\u4ef6\u4e8b\u7684\u8bc4\u4ef7;
It is+adj+of sb to do sth. adj\u5e94\u8be5\u662f\u5bf9\u505a\u8fd9\u4ef6\u4e8b\u7684\u4eba\u7684\u8bc4\u4ef7,adj\u591a\u7528\u5f62\u5bb9\u4eba\u7684.
\u2460It is +adj+for sb to do sth. \u5f62\u5bb9\u8bcd(for\u524d\u7684)\u662f\u591a\u7528\u6765\u5f62\u5bb9\u4e00\u4ef6\u4e8b\u60c5(\u52a8\u8bcd\u4e0d\u5b9a\u5f0f\u6240\u8868\u793a\u7684\u52a8\u4f5c),
\u5373\u4fee\u9970\u7684\u662f to do sth. adj\u662fdo sth.\u7684\u5c5e\u6027; sb.\u8ddfadj.\u6ca1\u6709\u76f4\u63a5\u8054\u7cfb. for\u662f\u6307\u5e72\u8c0b\u4e8b\u4f1a\u5982\u4f55.
It's plesant for us to take a walk after supper.
\u2461It is+adj+of sb to do sth. \u5f62\u5bb9\u8bcd(of\u524d\u7684)\u662f\u591a\u7528\u6765\u5f62\u5bb9\u4eba\u7684;\u4fee\u9970\u7684\u662f\u4ecb\u8bcdof\u540e\u9762\u63a5\u7684\u5bbe\u8bed. sb.\u8ddfadj.
\u6709\u76f4\u63a5\u8054\u7cfb.
\u2462\u5b9e\u4f8b\u8fa8\u6790:
It's very difficult for me to do it. (difficult \u6307\u4e8b\u60c5\u5f88\u96be)
It's very kind of you to do it for me. (kind\u6307\u4eba\u7684\u54c1\u8d28\u597d)
It is more convenient for him to walk directly.\u5bf9\u4ed6\u6765\u8bf4,\u76f4\u63a5\u8d70\u8fc7\u6765\u6bd4\u8f83\u4fbf\u6377. (convenient \u6307\u4e8b\u60c5\u5f88\u4fbf\u6377)
It is clever of him to come down without ropes.\u4ed6\u5f88\u806a\u660e,\u4e0d\u7528\u7ef3\u5b50\u5c31\u80fd\u4e0b\u6765. (convenient \u6307\u6307\u4eba\u5f88\u806a\u660e)
2.\u903b\u8f91\u7ed3\u6784\u4e0a\u7684\u533a\u522b:
\u65b9\u6cd5:\u53d6\u4ecb\u8bcdof/for\u540e\u7684\u4ee3\u8bcd\u4f5c\u903b\u8f91\u4e3b\u8bed\u548c\u4ecb\u8bcd\u524d\u8fb9\u7684\u5f62\u5bb9\u8bcd\u4f5c\u8868\u8bed,\u9020\u4e2a\u53e5\u5b50.
\u53e5\u5b50\u7ed3\u6784:\u201c\u903b\u8f91\u4e3b\u8bed+be+\u5f62\u5bb9\u8bcd\u201d.\u5373:sb.is adj to do sth (\u4e0d\u5b9a\u5f0f\u4f5c\u53e5\u5b50\u7684\u72b6\u8bed).
\u5982\u679c\u9053\u7406\u4e0a\u901a\u987a\u7528of,\u4e0d\u901a\u5219\u7528for.\u5982:
It is good for you to look at this book. \u662f\u8bf4: ....\u5bf9\u4f60\u6709\u597d\u5904. \u770b\u8fd9\u672c\u4e66\u5bf9\u4f60\u6709\u597d\u5904.
It is nice of you to give me such advice.\u662f\u8bf4: \u4f60\u5f88\u597d,\u611f\u6fc0\u4f60\u7ed9\u6211\u63d0\u4f9b\u5efa\u8bae.
*\u63d0\u53d6\u903b\u8f91\u4e3b\u8bed\u548c\u5f62\u5bb9\u8bcd\u9020\u53e5:
It is nice of you to help me. \u63d0\u53d6you\u4e0enice \u53ef\u6784\u6210you are nice. (\u901a\u987a,\u6240\u4ee5\u5e94\u7528of).
It's very kind of you to help me. \u63d0\u53d6you\u4e0ekind\u53ef\u6784\u6210you are kind. (\u901a\u987a,\u6240\u4ee5\u5e94\u7528of).
It is good for you to look at this book.\u63d0\u53d6you\u4e0egood\u53ef\u6784\u6210you are good(\u6709\u597d\u5904\u7684). (\u4e0d\u901a,\u6240\u4ee5\u5e94\u7528for)
It is hard for him to study two languages. \u63d0\u53d6he\u4e0ehard\u53ef\u6784\u6210he is hard(\u56f0\u96be\u7684). (\u4e0d\u901a,\u6240\u4ee5\u5e94\u7528for)
\u56db.\u6ce8\u610f:
of sb. \u7684\u53e5\u578b\u901a\u5e38\u90fd\u53ef\u8f6c\u6362\u4e3a\u4e0d\u5b9a\u5f0f\u4f5c\u72b6\u8bed\u7684\u53e5\u5b50,\u4f46for sb.\u53e5\u578b\u4e0d\u53ef\u4ee5.
It\u2019s very nice of you to offer me a seat.
= You are nice to offer me a seat. \u5341\u5206\u611f\u8c22\u4f60\u7ed9\u6211\u8ba9\u5ea7.
It is careless of him to lose so many things.
= He is careless to lose so many things. \u4ed6\u4e22\u4e86\u8fd9\u4e48\u591a\u4e1c\u897f,\u771f\u662f\u592a\u7c97\u5fc3\u4e86.
It\u2019s very important for you to practise your oral English in daily life.

it is ...for sb. to do 和it is ...of sb. to do在中文中都有表达某人在某事上的表现情况，但在英文中表达的侧重点是有所不同的，具体如下：

1.这两个单词的常用搭配都是 it is +形容词+for+sb. to do...和it is +形容词+of sb. to do...，但是根据所接的形容词类别不同，表达的意思也不同。

2.如果所接的是表示行为者的性格、品质等特点的。常见的有：kind,  good, nice, wrong, clever, careless, polite, foolish等。那么就要使用it is ...of sb. to do..如例句：

It's  kind of you to help me.你能帮助我真是太好了（强调的是行为者乐于助人的好品质。）

3.如果所接的是仅仅是描述事物的特点，而不是对行为者品格进行评价的（即普通的形容词语），如difficult,easy,hard,important等用一般采用it is ...for sb. to do...这个结构。如例句：

It's important for us to study English.学习英语对我们很重要。（强调的是学习英语这件事情）

4.总的来说，for sb.的结构是指这件事对于某人的作用或意义，而of sb.的结构是指发言者对行为者的主观评价和看法。

扩展资料：

这两个词最比较好用的辨别方法：如果be动词后的形容词是说明不定式的逻辑主语,就用of sb.to do...；如果是说明整个不定式的,则用 for sb.to do...；例如：

1.It is very kind of you to help us.（可以转换成：You are very kind to help us.kind
说明 you 的属性）；
2.It is possible for us to get there before dark.(不可转换成：we are possible...,而应该是 for us to get there is possible)

参考资料来源：for-百度翻译 of-百度翻译

1、It is +形容词+for sb. to do sth.这个句式里的形容词是用来描述事物的。如：

It is important for you to learn English.学习英语对于你来说很重要。

2、It is +形容词+of sb. to do sth.这个句式里的形容词是用来描述事物的。如：

It is nice of you to help me.你能帮助我太好了。

扩展资料：

若要说明动词不定式的动作是谁做的，可在形容词后加上for sb这样的介词短语，

即形成“It is + 形容词 + for sb+ to do sth”这样的结构，意思是“对某人来说，做某事怎么

样”。其中sb与动词不定式之间存在逻辑上的主谓关系。如：

It’s good for the students to do eye exercises twice a day.

对学生来说，一天做两次眼保健操是有益处的。

在此结构中，形容词是对做这件事(即动词不定式所表示的动作)的评价，与sb没有直接联系，

因此常用easy, difficult, hard, important, necessary,(im)possible等形容词。又如：

It is hard for us to finish the work in an hour.

要我们在一小时之内完成工作很难。

it is ...for sb. to do 和it is ...of sb. to do在中文中都有表达某人在某事上的表现情况，但在英文中表达的侧重点是有所不同的，具体如下：

1.这两个单词的常用搭配都是 it is +形容词+for+sb. to do...和it is +形容词+of sb. to do...，但是根据所接的形容词类别不同，表达的意思也不同。

2.如果所接的是表示行为者的性格、品质等特点的。常见的有：kind,  good, nice, wrong, clever, careless, polite, foolish等。那么就要使用it is ...of sb. to do..如例句：

It's  kind of you to help me.你能帮助我真是太好了（强调的是行为者乐于助人的好品质。）

3.如果所接的是仅仅是描述事物的特点，而不是对行为者品格进行评价的（即普通的形容词语），如difficult,easy,hard,important等用一般采用it is ...for sb. to do...这个结构。如例句：

It's important for us to study English.学习英语对我们很重要。（强调的是学习英语这件事情）

4.总的来说，for sb.的结构是指这件事对于某人的作用或意义，而of sb.的结构是指发言者对行为者的主观评价和看法。

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扩展资料：

这两个词最比较好用的辨别方法：如果be动词后的形容词是说明不定式的逻辑主语,就用of sb.to do...；如果是说明整个不定式的,则用 for sb.to do...；例如：

1. It is very kind of you to help us.（可以转换成：You are very kind to help us.kind说明 you 的属性）；2.It is possible for us to get there before dark.(不可转换成：we are possible...,而应该是 for us to get there is possible)

1）若形容词为描述不定式行为者的性格、品质的，如kind,good,nice,right,wrong,clever,careless,polite,foolish等用of sb。
例如：
It's very king of you tu help me.你能帮我真好。

(2)若形容词仅仅是描述事物，不是不定式行为者的品格进行评价的，如difficult,easy,hard,important,dangerous,possible等用for sb。
例如：
2.It is very important for us to master English.

."It is＋形容词＋of sb.to do sth.."和"It is＋形容词＋for sb.to do sth.."这两个句型使用频率都很高。前者表示说话人对客观事物的高兴、惊讶、遗憾、难过等情绪，表现的是人的性格、品质或特征，经常可以转换成：①How＋形容词＋it is＋of sb.to do sth.！②How＋形容词＋of sb.to do sth.！③Sb.＋is＋形容词＋to do sth..或④That is＋形容词＋of sb.to do sth.等；后者表示说话人对客观事件的决断性，根据具体情况可以转换成：①To do sth.is＋形容词；②It is＋形容词＋that从句。如：
　　It is possible to work out whether you will save or lose money by increasing the temperatureby1℃.(利用计算机)能够计算出温室里的温度升高一度会使你赚钱还是赔钱。

　　Is it necessary to complete the design before National Day?在国庆节前完成这一设计有必要吗？

　　It is stupid of him to refuse the invitation.他拒绝了邀请，真是件错事。

　　上一句可转换成：How stupid it is of him to refuse the invitation!

　　或How stupid of him to refuse the invitation!

　　或He is stupid to refuse the invitation.

　　It is better for you to live alone for sometime.你单独住一段时间更好。

　　上一句可转换成：To live alone for sometime is better.

　　或It is better that you live alone for sometime.

若形容词是描述不定式行为者的性格、品质的，如kind，good，nice，right，wrong，clever，careless，polite，foolish等，用of sb.。

It’s very kind of you to help me. 你能帮我，真好。

It’s clever of you to work out the maths problem.
你真聪明，解出了这道数学题。

若形容词仅仅是描述事物，不是对不定式行为者的品格进行评价，用for sb.，这类形容词有difficult，easy，hard，important，dangerous，（im）possible等。

It’s very dangerous for children to cross the busy street.
对孩子们来说，穿过繁忙的街道很危险。

It’s difficult for us to finish the work. 对我们来说，完成这项工作很困难。

注 意 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

of sb. 的句型通常都可转换为不定式作状语的句子，但for sb. 句型不可以。

It’s very nice of you to offer me a seat.

= You are nice to offer me a seat. 十分感谢你给我让座。

It is careless of him to lose so many things.

= He is careless to lose so many things. 他丢了这么多东西，真是太粗心了。

It’s very important for you to practise your oral English in daily life.
在日常生活中练习你的英语口语非常重要的。

这句话不能说成：It is very important of you to practise…

It is+adj.+of sb. +to do sth中的adj.跟sb.有关,
这个adj.是用来形容sb.的,
表示某人这么做真是太adj.了．
你会发现在这个句型中你把sb.和adj.提出来可以造个句sb. is(are) adj.
如It's very kind of you to help me.
把里面的sb.和adj.提出来可以发现you are kind是说得通的.

而It is +adj.+for sb.+to do sth表示做某事对某人来说很adj.
这里的adj.是do sth.的属性
里面的sb.跟adj.没有直接联系
如It's difficult for you to deal with the problem.
你就不能说you are difficult了吧

这就是怎么决定句子中的介词用of还是用for的方法

扩展阅读：it is adj for sb to ... it is of great necessity ... it is n for sb to do ... itsadjofsb to do sth ... it is time for sb ... its stupid of sb ... inappropriate ... considerable ... it is up to you ...