托福备考中，词汇是一个很终于要的环节，之前我们讲了一下不定式作宾语、主语，下面接着讲一下不定式作表语。

   作表语：当句子的主语是purpose, aim, duty, goal, hope, plan, suggestion, idea, intention, problem, mistake, reaction等表示“意图”、“目的”、“功能”等意思的词时，一般由不定式作表语 

　　如：His only purpose in life is to seek truth. 

　　Our plan was to raise money for the new project. 

　　例题： 

　　(1) 

　　Before the invention of the clock, people had to reliable on the celestial bodies to tell time. 

　　应改为：rely. 

　　解释：此处to是构成不定式的标志词, 之后应接动词原形 

　　(2) 

　　Chinese immigrants began ---- to the United States in large numbers in the middle of the nineteenth century. 

　　(A) come 

　　(B) to come 

　　(C) to have come 

　　(D) have come 

　　答案：B 

　　解释：空格处需要began的宾语，可以是动名词或不定式，A, D是动词原形，可先排除；C是不定式的完成式，不符合begin的用法；只有B正确 

　　(3) 

　　The central purpose of management is for making every action or decision help achieve a carefully chosen goal. 

　　应改为：to make 

　　解释：主语purpose决定应用不定式作表语，故改为to make 。