关于can / could后接不式的用法分析

That day Mr Smith got up late, so he ran as fast as he could _________ the early bus.

A. catch                  B. to catch               C. catching              D. caught

【分析】此题容易误选A，认为情态动词后只能接动词原形。但是，错了，正确的答案是B。其实情态动词 could 后本来有动词原形 run，只是被省略了，即此句的完整形式应是 …so he ran as fast as he could run to catch the early bus，其中的不定式 to catch the early bus 为目的状语。又如：

(1) My parents did what they could _________ my aunt and uncle.

A. help                    B. to help                    C. helping                 D. helped

(2) He read what he could _________ his knowledge.

A. widen                  B. to widen                 C. widening              D. widened

以上两题均选B，即选不定式，且此不定式为目的状语。但是，同学们若据此形成思维定势，也会麻烦。为此，请再看两题：

(1) He ran as fast as he could _________to catch the bus.

A. hope                  B. to hope                   C. hoping                   D. hoped

【分析】此题的最佳答案不是B，而是C，其中的现在分词短语 hoping to catch the bus 用作伴随状语，即一边跑一边在希望能赶上早班车。(from www.nmet168.com)

(2) He spent every minute he could _________ foreign languages.

A. study                 B. to study                   C. studying                D. studied

【分析】此题也应选C，但是，它与上题选现在分词 hoping 表伴随有所不同，此题的 studying 其实与其前的动词 spend 有关，即此句中的 studying 为动名词，其前省略了介词 in。注意spend 的句型：spend + 时间或金钱 + (in) doing sth。