(3) A hinge joint is ------- permits the forward and backward movement of a door。

　　(A) the

　　(B) what

　　(C) those

　　(D) whose (88.10)

　　［答案］ B what = the thing that…

　　(4) Essentially， a theory is an abstract. Symbolic representation of ------- reality。

　　(A) what it is conceived

　　(B) that is conceived

　　(C) what is conceived to be

　　(D) that is being conceived of (89.5)

　　［答案］ C what = the thing that (is conceived to be…) 。答案(A)中的代词it是多余的，因为what本身即已包含了先行词(the thing ) 和关系代词(that) 。答案(B)中的关系代词that引导的从句不可以置于介词的后面。

　　(5) Most of the food what elephants eat is brought to their mouths by their trunks. (93.10

　　［答案］ B what应改为that。此句已含有先行词food，不能再用关系代词what。

　　5. 主句和从句

　　解题要点 主语从句是TOEEL常考而中国考生又较陌生英文文法结构。有关主语从句的命题几乎全部集中在structure (1-15题)中。主语从句的特点是读起来有种头重脚轻的感觉，而且有两个谓语动词。连词That 引导的主语从句应特别留意。因为That 在句中没有任何意义，它只具有引导出主语从句的功能，因而很容易被忽略。

　　全真例题分析

　　(1) ------- xenon could not from chemical compounds was once believed by scientists。

　　(A) For

　　(B) It was

　　(C) That

　　(D) While (91.1)

　　［答案］ C That引导的主语从句。其中第一个谓语动词could from 是从句的谓语，第二个系动was是主句的谓语。

　　(2) ------- to space travelers is high acceleration of deceleration forces。

　　(A) Danger can be

　　(B) They can be dangerous

　　(C) What can be dangerous

　　(D) While danger (93.1)

　　［答案］ C what引导的主语从句。What既是从句的连词，又是从句的主语。

　　(3) ------- has been a topic of continual geological research。

　　(A) Did the continents originate

　　(B) How did the continents originate

　　(C) Have the continents originated

　　(D) How the continents originated (91.1)

　　［答案］ D How 引导的主语从句。

　　(4) ------- progress helps to relieve scarcities is a fact accepted by economists。

　　(A) Technological

　　(B) That technological

　　(C)Although technological

　　(D)There is technological