It做形式主语时其后 to do 和 ing 的不同用法 及具体例句 用it做形式主语时，用ing还是用ed？
it\u4ec0\u4e48\u65f6\u5019\u505a\u5f62\u5f0f\u4e3b\u8bed it\u505a\u5f62\u5f0f\u4e3b\u8bed\u65f6\u540e\u7684\u52a8\u8bcd\u7528\u4e0d\u5b9a\u5f0f\u8fd8\u662fing\u5f53\u4e0d\u5b9a\u5f0f\u77ed\u8bed\u3001\u52a8\u540d\u8bcd\u77ed\u8bed\u548c\u4ece\u53e5\u4f5c\u4e3b\u8bed\u65f6\uff0c\u4e3b\u8bed\u90e8\u5206\u7684\u957f\u5ea6\u603b\u662f\u8d85\u8fc7\u8c13\u8bed\u90e8\u5206\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u5982\u679c\u4ecd\u65e7\u628a\u4e3b\u8bed\u653e\u5728\u8c13\u8bed\u52a8\u8bcd\u524d\uff0c\u53e5\u5b50\u5c31\u4f1a\u663e\u5f97\u5934\u91cd\u811a\u8f7b\u3002\u4e3a\u4e86\u8c03\u8282\u53e5\u5b50\u7684\u5e73\u8861\uff0c\u4e8e\u662f\u5c31\u628a\u4e3b\u8bed\u653e\u5728\u8c13\u8bed\u90e8\u5206\u7684\u540e\u9762\uff0c\u539f\u4e3b\u8bed\u7a7a\u7f3a\u7684\u4f4d\u7f6e\u7531\u5f62\u5f0f\u4e3b\u8bedit \u5145\u5f53\u201c\u5080\u5121\u201d\uff0c\u800c\u771f\u6b63\u7684\u4e3b\u8bed\u5219\u5728\u201c\u540e\u5bab\u5782\u5e18\u542c\u653f\u201d\u3002
\u5f62\u5f0f\u4e3b\u8bed\u7528\u4e8e\u4e09\u79cd\u60c5\u51b5\u3002
\u3000\u30001\u3001\u5982\u679c\u8868\u8bed\u662f\u8868\u793a\u201c\u597d\u5904\u201d\u6216\u201c\u7528\u5904\u201d\u7684\u5f62\u5bb9\u8bcd\u6216\u540d\u8bcd\u65f6\uff0c\u8981\u7528\u52a8\u540d\u8bcd\u77ed\u8bed\u4f5c\u4e3b\u8bed\u3002\u5e38\u7528\u7684\u5f62\u5bb9\u8bcd\u6709 good, helpful, helpless, useful, useless \u7b49\uff0c\u540d\u8bcd\u6709 no good, no use, no help \u7b49\u3002\u5982\uff1a
It is helpful having you in the room when major news is expected. \u7b49\u5f85\u91cd\u5927\u6d88\u606f\u65f6\u6700\u597d\u6709\u4f60\u4eec\u5728\u573a\u3002
It's nouse praying for the weather to change. \u7948\u7977\u5929\u6c14\u8f6c\u53d8\u662f\u5f92\u52b3\u7684\u3002
\u3000\u30002. \u5982\u679c\u8868\u8bed\u662f\u5176\u4ed6\u5f62\u5bb9\u8bcd\u6216\u540d\u8bcd\uff0c\u5219\u7528\u4e0d\u5b9a\u5f0f\u77ed\u8bed\u4f5c\u4e3b\u8bed\u3002\u5176\u7ed3\u6784\u662f\u201cIt + \u7cfb\u52a8\u8bcdbe +\u8868\u8bed + (for sb.) to do sth\u201d\u3002\u5982\uff1a
It is important (for sb.) to do sth. \uff08\u67d0\u4eba\uff09\u505a\u67d0\u4e8b\u5f88\u91cd\u8981\u3002
It is necessary for sb. to do sth. \u67d0\u4eba\uff09\u505a\u67d0\u4e8b\u5fc5\u8981\u7684
It was unfair to (for sb.) to do sth.\uff08\u67d0\u4eba\uff09\u505a\u67d0\u4e8b\u662f\u4e0d\u516c\u5e73\u7684\u3002
It was an effort (for sb.) to do sth.. \uff08\u67d0\u4eba\uff09\u505a\u67d0\u4e8b\u662f\u4ef6\u8d39\u52b2\u7684\u4e8b\u3002
It mustbe a good job (for sb.) to do sth.. \uff08\u67d0\u4eba\uff09\u505a\u67d0\u4e8b\u662f\u4ef6\u597d\u4e8b\u3002
\u3000\u3000\u9664\u6b64\u4e4b\u5916\uff0c\u5982\u679c\u8868\u793a\u201c\u4ed8\u51fa\u65f6\u95f4\u3001\u91d1\u94b1\u6216\u7cbe\u529b\u7b49\u505a\u67d0\u4e8b\u201d\uff0c\u4e5f\u8981\u7528\u4e0d\u5b9a\u5f0f\u77ed\u8bed\u4f5c\u4e3b\u8bed\uff0c\u5176\u7ed3\u6784\u662f\u201cIt + take/cost + sb. + time/money/effort + to do sth\u201d\u3002\u5982\uff1a
It took/cost him two hours to do his homework. \u505a\u4f5c\u4e1a\u82b1\u4e86\u4ed6\u4e24\u4e2a\u5c0f\u65f6\u3002
It took/cost me over $ 6 to buy the suit. \u4e70\u90a3\u4ef6\u8863\u670d\u82b1\u6389\u62116\u82f1\u9551\u3002
It took him a hard work to pay off the debt. \u8fd8\u6e05\u8fd9\u7b14\u503a\u52a1\u82b1\u8d39\u4e86\u4ed6\u8f9b\u52e4\u52b3\u52a8\u3002
\u3000\u3000\u3010\u6ce8\uff1a\u5982\u679c\u8868\u8bed\u662f worth while\uff0c\u65e2\u53ef\u4ee5\u7528\u4e0d\u5b9a\u5f0f\u4e5f\u53ef\u4ee5\u7528\u52a8\u540d\u8bcd\u4f5c\u4e3b\u8bed\u3002\u4f8b\u5982 It is worth while to discuss [discussing] the problem. \u8fd9\u4e2a\u95ee\u9898\u503c\u5f97\u8ba8\u8bba\u4e00\u4e0b\u3002\u3011
\u3000\u30003\u3001\u201cIt + \u7cfb\u52a8\u8bcdbe +\u8868\u8bed + for sb. to do sth\u201d\u8fd9\u79cd\u7ed3\u6784\u4e5f\u53ef\u4ee5\u6539\u7528\u4e3b\u8bed\u4ece\u53e5\uff0c\u7ed3\u6784\u4e3a\u201cIt + \u7cfb\u52a8\u8bcdbe +\u8868\u8bed + \u4e3b\u8bed\u4ece\u53e5\u201d\u3002\u5982\u679c\u5f3a\u8c03\u201c\u67d0\u4eba\u5e94\u8be5\u505a\u67d0\u4e8b\u201d\u662f\u8bf4\u8bdd\u4eba\u7684\u4e2a\u4eba\u770b\u6cd5\uff0c\u5219\u4ece\u53e5\u9700\u8981\u7528\u865a\u62df\u8bed\u6c14\uff08should\u5e38\u5e38\u7701\u7565\uff09\u3002\u5982\uff1a
It is important that he (should) complete the task in time. \u4ed6\u53ca\u65f6\u5b8c\u6210\u8be5\u9879\u4efb\u52a1\u662f\u5f88\u91cd\u8981\u7684\u3002
It was necessary that they (should) come earlier. \u4ed6\u4eec\u5f88\u6709\u5fc5\u8981\u63d0\u65e9\u4e00\u4e9b\u6765\u3002
\u9996\u5148\uff0cit\u4e0d\u662ftake\u7684\u903b\u8f91\u4e3b\u8bed\u3002\u5982\u679c\u628a\u6761\u4ef6\u72b6\u8bed\u6539\u6210\u4ece\u53e5\uff0c\u771f\u6b63\u88ab\u7701\u7565\u7684\u4e3b\u8bed\u662fwe\uff1a
If we take all these factors into consideration, it is natural to draw such a conclusion that as far as his age is concerned, Tom is an excellent boy.
\u90a3\u4e48\u8fd9\u79cd\u60c5\u51b5\u4e0b\u5e94\u8be5\u7528\u73b0\u5728\u5206\u8bcd\uff0c\u800c\u4e0d\u662f\u8fc7\u53bb\u5206\u8bcd\uff1a
Taking all these factors into consideration, it is natural to draw such a conclusion that as far as his age is concerned, Tom is an excellent boy.
\u53e5\u5b50\u7ed3\u6784\uff1a
Taking all these factors into consideration \u6761\u4ef6\u72b6\u8bed
it \u5f62\u5f0f\u4e3b\u8bed\uff0c\u6307\u4ee3\u540e\u7f6e\u7684\u4e3b\u8bed\u4e0d\u5b9a\u5f0fto draw such a conclusion
is \u7cfb\u52a8\u8bcd
natural \u8868\u8bed
to draw such a conclusion \u4e3b\u8bed
that (as far as his age is concerned,) Tom is an excellent boy. \u540c\u4f4d\u8bed\u4ece\u53e5\u8bf4\u660econclusion
as far as his age is concerned \u540c\u4f4d\u8bed\u4ece\u53e5\u4e2d\u7684\u72b6\u8bed\u4ece\u53e5
\u7528\u8fc7\u53bb\u5206\u8bcd\u77ed\u8bed\u4f5c\u72b6\u8bed\uff0c\u5206\u8bcd\u77ed\u8bed\u7684(\u88ab\u52a8\u8bed\u6001)\u903b\u8f91\u4e3b\u8bed\u901a\u5e38\u4e5f\u662f\u4e3b\u53e5\u7684\u4e3b\u8bed\u3002\u5982\uff1a
Taken into consideration, all these factors lead us to draw such a conclusion that as far as his age is concerned, Tom is an excellent boy.
\u8fd9\u53e5\u76f8\u5f53\u4e8e\uff1a
If all these factors are taken into consideration, they lead us to draw such a conclusion that as far as his age is concerned, Tom is an excellent boy.
\u521a\u624d\u684c\u5b50\u4e0a\u6709\u4e00\u5f20\u6211\u6700\u559c\u6b22\u7684\u7535\u5f71\u660e\u661f\u6d77\u62a5\u3002
A poster of my favorite movie star was on the table just a moment ago.
\u5982\u679c\u7528\u4f60\u7684\u8868\u8fbe\u65b9\u5f0f\uff1a
A poster with my favorite movie star on it was on that table just now.
\u6ce8\u610f\uff1a
1. on\u540e\u9762\u4e00\u5b9a\u8981\u8ddf\u5bbe\u8bed\u3002
2. just now\u8868\u793a\u7684\u610f\u601d\u6bd4\u201d\u521a\u624d\u201d\u8fd8\u8981\u63a5\u8fd1\u73b0\u5728\uff0c\u662f\u73b0\u5728\u7684\u4e00\u77ac\u95f4\u4e4b\u524d\u3002\u9664\u975e\u8fd9\u662f\u4f60\u8981\u8868\u8fbe\u7684\u610f\u601d\uff0c\u8fd8\u662f\u7528just a moment ago\u66f4\u597d\u4e9b\u3002
动词不定式在句中可以作主语，如：
To err is human, to forgive devine.
To see is to believe.
To do that implies taking responsibility.
当代英语常常用it作形式主语，把动词不定式放在谓语之后。
It takes ten people to encircle the big tree,
How long did it take you to finish the work?
动名词在句子中也可以作主语，其逻辑主语泛指人们：
Seeing is believing.
Saving is having,
it作形式主语，把真正的主语——动名词放在句末的情况比较少，常用的结构有：it is后接no use，no good、fun等名词，如：
It is no use crying over spilt milk.
It is no good objecting.
It is great fun sailing a boat.
it is后还可接useless、nice、good、interesting等形容词。如：
It is useless speaking.
It is so nice sitting here with you.
It is good hearing English spoken.
It作形式主语时，位于谓语之后作真实主语的非谓语动词以不定式为多，除了在上述名词和形容词后面用动名词以外，一般都用动词不定式作真实主语。希望我能帮助你解疑释惑。
it做形式主语后面通常情况是跟to do.没怎么看到用doing 的。例如：It's+adj. for/of sb. to do sth.
It's important for you to study English well. It's kind of you to help me.
it is +noun for sb to do sth
for example, it is time for the government to take some measures
扩展阅读：with something to do ... 主语加形容词加to do ... it 作为形式主语的用法 ... it 做形式主语的用法 ... it做形式宾语6123原则 ... be invited to ... 形式主语to do ... it is senseless doing ... it做形式主语的知识点 ...
