英语思维定势错误例析——情态动词后接非谓语动词
一般说来，情态动词后面需要接动词原形，不可以接不定式、目前分词之类的非谓语动词，以could为例举比如下：
This man could heal all diseases. 这个人什么病都能治。
I could hardly wait to hear the news. 我简直等不及听那个消息了。
We could hear her feet right above us. 大家能听到正上方她的脚步声。
但请看下面一题，千万不要思维思势的影响做错了：
The soldiers tried their best and did what they could _________ against the flood.
A. fight B. to fight C. fighting D. fought
有些同学一看到空格前的情态动词 could 就判定此处应填动词原形 fight，即判定选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 。即句中的不定式短语用作目的状语的，而不是与情态动词一块构成谓语。请再看类似例句：
He did what he could to help us. 他尽力帮助大家。
He saved what he could to buy a car. 他尽可能节省每一分钱以便买车。
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，有些同学可能又会想当然地觉得，以后只须遇见类似结构的题选带to不定式就万事大吉了，但也未必，例外还是有些，还要具体问题具体剖析。请看下例：
He ran as fast as he could _________ to catch the early bus.
A. to hope B. hope C. hoping D. hoped
若依据以上“经验”觉得此题要选A答案，那就又错了。此题应选 C，其中的目前分词短语 hoping to catch the early bus 用作随着状语。
He spent every minute he could _________ spoken English.
A. practise B. to practise C. practising D. practised
此题应选 C，它与以上各题的情形均有所不同，虽然与上面的第题的答案一样，均为动词的 –ing 形式，但也不完全一样：第的 hoping 为目前分词，在句中用作随着状语；而此题的 practising 是动名词，之所以用它与前面动词 spent 的搭配有关，即 spend …doing sth。若将此句补充完整，即为 He spent every minute he could spend in practising spoken English.
Mr Smith made up his mind to devote all he could _________ his oral English before going abroad.
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。
