情態動詞后為什么接帶to不定式

Now everyone here was working hard and doing what they could _______ more money.

A. make            B. to make             C. making           D. made

【答案與分析】

此題容易誤選A。有的同學一看到空格前的情態動詞 could 就斷定此處應填動詞原形 make。其實正確答案應是B，此句為省略句，即在 could 后省略了動詞 do，若把句子補完整應為Now everyone here was working hard and doing what they could do to make more money，即句中的不定式短語(to make more money)是用作目的狀語的，而不是與情態動詞(could)一起構成謂語。

【類似考題】

(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

以上兩題均選B，即選不定式，且此不定式為目的狀語。但是，同學們若據此形成思維定勢，也會麻煩。為此，請再看兩題：

(3) He ran as fast as he could ____to catch the bus.

A. hope             B. to hope

C. hoping         D. hoped

此題的最佳答案不是B，而是C，其中的現在分詞短語 hoping to catch the bus 用作伴隨狀語，即一邊跑一邊希望能趕上早班車。但是，如果選B，將 to hope to catch the bus 視為目的狀語行不行呢？不行。因為“他拼命地跑”目的是“為了趕上公共汽車”，而不是“為了希望趕上公共汽車”，換句話說，將“希望”作為“目的”不妥。因為同樣的原因，下面一題也應選 hoping：

He studied as hard as he could _____ to enter a good college.

A. hope             B. to hope

C. hoping         D. hoped

(4) He spent every minute he could ______ foreign languages.

A. study              B. to study

C. studying         D. studied

此題也應選C，但是，它與上題選現在分詞 hoping 表伴隨有所不同，此題的 studying 其實與其前的動詞 spend 有關，即套用的是“spend + 時間或金錢 + (in) doing sth”這一句型。