D 关系代词who引导定语从句，并作从句的主语。

（4）——。 Some of the Earth*s interior heat escapes to the surface.

（A） A volcano erupts

（B） A volcano whether erupts

（C） A volcano erupts it

（D） If a volcano erupts （93.5）

D 从属连词引导条件状语从句。

2. 关系代词 who与which混淆错用

解题要点：在written Expression （16-40题）中的四个选择答案中出现who 或者which，应确认它所指代的是人还是物。

全直例题分析

（1）Fossil remains indicate that squidlike creatures called belemnites swam in the sea who covered the North American continent 70 million years ago. （94.5）

C 关系代词who指代的是sea，因此应用指物的which或that.

（2）Vaccines for some rare diseases are given only to persons which risk exposure to the disease. （93.1）

B 关系代词which指代前面的persons，应改为人称关系代词who.

（3）Anne Elizabeth McDowell is best remembered for a weekly journal， the Woman*s Advocate， who she launched in January 1855. （91.8）

D 关系代词who指代杂志the woman*s Advocate，故应改为which.

（4） The attorney general of the United States advises the President on any questions of law who may arise in the conduct of administrative affairs. （90.10）

B 关系代词who指代前文的questions of law，故应改为which或that.

3. 介词＋关系代词which结构