Whose is this pen? 能帮我分析一下句型结构嘛？ 有大神能帮我分析一下第八句的句型结构吗？to relax 是...

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"But \u662f\u8fde\u8bcdit\u662f\u4e3b\u8bed didn't take \u662f\u8c13\u8bedvery long \u662f\u5bbe\u8bedbefore they discovered that the most important thing was the ability to send mail around\u662f\u72b6\u8bed\u4ece\u53e5\uff0c\u5176\u4e2dthat\u4ece\u53e5\u662f\u72b6\u8bed\u4ece\u53e5\u4e2d\u7684\u5bbe\u8bed\u4ece\u53e5, which they had not anticipated at all\u662f\u975e\u9650\u5236\u6027\u5b9a\u8bed\u4ece\u53e5\u4fee\u9970\u524d\u9762\u7684the ability,"
\u672c\u53e5\u610f\u601d\uff1a\u4f46\u662f\u6ca1\u8fc7\u591a\u4e45\uff0c\u4ed6\u4eec\u5c31\u53d1\u73b0\u6700\u91cd\u8981\u7684\u4e8b\u60c5\u662f\u80fd\u591f\u56db\u5904\u53d1\u9001\u90ae\u4ef6\uff0c\u8fd9\u5b8c\u5168\u51fa\u4e4e\u4ed6\u4eec\u7684\u610f\u6599\u3002

\u662f\u4e3b\u8bed\uff0c\u56e0\u4e3a\u8fd9\u662f\u4e3a\u4e86\u907f\u514d\u5934\u91cd\u811a\u8f7b\u800c\u7528it\u4f5c\u5f62\u5f0f\u4e3b\u8bed\uff0c\u539f\u6765\u5e94\u662fto relax by...is good\u3002

Whose is this pen?
Whose 是所有格疑问代词，作句子的表语。
is 是 be动词的三单形式，
this pen句子的主语。
此句是主系表结构的疑问句形式,
即 表语+be动词（或系动词）+主语 ？
也可以问成：This is whose pen? 或 Whose pen is this?

这个句子是错的。应该是Whose pen is this ?句子中间：This 是主语，is 是系动词，pen 作表语。whose 作定语，修饰钢笔。

扩展阅读：whose is this的回答 ... whose is this coat对吗 ... whose is this jacket ... here you are ... whose cap is this ... whose is this pen ... whose tail is that ... which one ... whose is this bag ...