The soldiers tried their best and did what they could _________ against the flood.
A. fight B. to fight C. fighting D. fought
有的同學(xué)一看到空格前的情態(tài)動(dòng)詞 could 就斷定此處應(yīng)填動(dòng)詞原形 fight，即斷定選A答案。其實(shí)選錯(cuò)了，正確答案應(yīng)是BA。這是一個(gè)省略句，即在 could 后省略了動(dòng)詞 do，若把句子補(bǔ)完整應(yīng)為The soldiers tried their best and did what they could do to fight against the flood (士兵們竭盡全力抗洪)。即句中的不定式短語 (to fight against the flood) 用作目的狀語的，而不是與情態(tài)動(dòng)詞(could)一起構(gòu)成謂語。請(qǐng)?jiān)倏搭愃评洌?/p>
(1) He did what he could to help us. 他盡力幫助我們。(2) He saved what he could to buy a car. 他盡量節(jié)約每一分錢以便買車。(3) He ran as fast as he could to catch the early bus. 他拼命地跑以便趕上早班車。
至此，有的同學(xué)可能又會(huì)想當(dāng)然地認(rèn)為，今后只要遇到類似結(jié)構(gòu)的題選帶to不定式就萬事大吉了，但也不一定，例外還是有的，還得具體問題具體分析。請(qǐng)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
若根據(jù)以上“經(jīng)驗(yàn)”認(rèn)為此題要選A答案，那就又錯(cuò)了。此題應(yīng)選 C，其中的現(xiàn)在分詞短語 hoping to catch the early bus 用作伴隨狀語。
(5) He spent every minute he could _________ spoken English.
A. practise B. to practise C. practising D. practised
【分析】此題應(yīng)選 C，它與以上各題的'情形均有所不同，雖然與上面的第(4)題的答案一樣，均為動(dòng)詞的 –ing 形式，但也不完全一樣：第(4) –ing 的 hoping 為現(xiàn)在分詞，在句中用作伴隨狀語；而此題的 practising 是動(dòng)名詞，之所以用它與前面動(dòng)詞 spent 的搭配有關(guān)，即 spend … (in) doing sth。
(6) Mr Smith made up his mind to devote all he could _________ his oral English before going abroad. A. improveA.B. to improve C. improving D. to improving
【分析】此題答案選D，注意兩點(diǎn)：一是 devote … to … 是固定搭配，意為“把……貢獻(xiàn)給……”；二是其中的 to 是介詞，不是不定式符號(hào)，后接動(dòng)詞時(shí)要用動(dòng)名詞。
