1. Everyone in our class was working hard and doing what we could_______ a good college.
A. enter B. to enter
C. entering D. entered
【陷阱】容易误选 A。有的同学一看到空格前的情态动词 could就断定此处应填动词原形 enter。
【分析】其实正确答案应是 B。此句为省略句，即在 could后省略了动词 do，若把句子补完整应为 Everyone in our class was working hard and doing what we could do to enter a good college。即句中的不定式短语( to enter a good college)是用作目的状语的，而不是与情态动词 (could)一起构成谓语。请再看类似例句：
( 1) They did what they could to comfort her. 他们尽量安慰她。
( 2) They did everything they could to save her life. 他们尽一切力量拯救她的性命。
( 3) He studies as hard as he could to catch up with his classmates. 他拼命学习以便赶上他的同学。
值得指出的是，这也并不是说今后只要遇到类似结构的题就一定选带 to不定式。请看以下试题：
( 4) He ran as fast as he could_____ to catch the early bus.
A. to hope B. hope
C. hoping D. hoped
此题的答案是 C不是 A，其中的现在分词短语 hoping to catch the early bus用作伴随状语。
( 5) He spent every minute he could_____ spoken English.
A. practise B. to practise
C. practising D. practised
此题答案选 C，这与前面动词 spent的搭配有关，即 spend… (in) doing sth。若将此句补充完整，即为 He spent every minute he could spend in practising spoken English.
( 6) Before going abroad he devoted all he could____ D____ his oral English.
A. improve B. to improve
C. improving D. to improving
此题答案选 D，注意两点：一是 devote… to…是固定搭配，意为“把……贡献给……”;二是其中的 to是介词，不是不定式符号，后接动词时要用动名词。
2. He knows nothing about it, so he can’ t help_______ any of your work.
A. doing B. to do
C. being doing D. to be done
【陷阱】容易误选 B，根据 can’ t help doing sth这一结构推出。
【分析】其实答案应选 A。比较以下结构：
can’ t help to do sth=不能帮助做某事
can’ t help doing sth=禁不住做某事，情不自禁地做某事
又如下面一题，答案也是 B：
She can’ t help____ the house because she’s busy making a cake.
A cleaning B. to clean
C. cleaned D. being cleaned
再请看以下试题：
While shopping, people sometimes can’ t help_____ into buying something they don’ t really need.
A. to persuade B. persuading
C. being persuaded D. be persuaded
此题应选 C，句中的 can’ t help意为“禁不住”(注意根据句意用被动形式)。
3. All her time_______ experiments, she has no time for films.
A. devoted to do B. devoted to doing
C. devoting to doing D. is devoted to doing
【陷阱】几个干扰项均有可能误选。
【分析】此题最佳答案为 B。现分析如下：
( 1) devote意为“致力于，献身于”，主要用 devote… to…或 be devoted to，其中的 to是介词，不是不定式符号，故后接动词时要用动名词，不用不定式。
( 2)选 A错误：若将 do改为 doing则可以。
( 3)选 B正确： all her time devoted to doing experiments为独立主格结构，用作状语。
( 4)选 C错误：因为 all her time与 devote为被动关系，故应将 devoting改为 devoted。
( 5)选 D错误：若单独看 All her time is devoted to doing experiments，此句并没有错，但问题是逗号前后两个简单句没有必要的连接方式，所以从整体上看仍不对，假若在后一句的句首加上 and或 so，则可选 D，或将 D将中的 is改为 being也可选它。
请做以下类似题(答案均选 A)：
( 1) All the preparations for the project______, we’re ready to start.
A. completed B. have been completed
C. had been completed D. been completed
( 2) Such_______ the case, I couldn’ t help but______ him.
A. being, support B. was, support
C. has been, supporting D. is, to support
比较以下各题，答案选 B，因为句中使用了并列连词 and：
( 1) All the preparations for the project______, and we’re ready to start.
A. completed B. have been completed
C. had been completed D. been completed
( 2) Such_______ the case, I couldn’ t help but______ him.
A. being, support B. was, support
C. has been, supporting D. is, to support
