有这样一道题，我们先来看看：　　

The soldiers tried their best and did what they could _________ against the flood.　　

A. fight                        B. to fight                        C. fighting                        D. fought　　

【分析】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 fight，即断定选A答案。其实选错了，正确答案应是B。这是一个省略句，即在 could 后省略了动词 do，若把句子补完整应为The soldiers tried their best and did what they could do to fight against the flood (士兵们竭尽全力抗洪)。即句中的不定式短语 (to fight against the flood) 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) He did what he could to help us. 他尽力帮助我们。　　

(2) He saved what he could to buy a car. 他尽量节约每一分钱以便买车。　　

(3) He ran as fast as he could to catch the early bus. 他拼命地跑以便赶上早班车。　　

至此，有的同学可能又会想当然地认为，今后只要遇到类似结构的题选带to不定式就万事大吉了，但也不一定，例外还是有的，还得具体问题具体分析。请看下例：　　

(4) He ran as fast as he could _________ to catch the early bus.　　

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

若根据以上“经验”认为此题要选A答案，那就又错了。此题应选 C，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　　

【分析】此题应选 C，它与以上各题的情形均有所不同，虽然与上面的第(4)题的答案一样，均为动词的