Question

He ________ sleep, although he tried to when he got on such a hunt for an idea until he had caught it.

A．wouldn't  B．shouldn't  C．couldn't  D．mustn't

Answer 1

 C�？疾榍閼B(tài)動(dòng)詞。從although he tried to可判斷出，他試圖想睡，但又睡不著，wouldn’t 不愿意，shouldn’t 不該，mustn’t含有禁止的意思，couldn’t不能，故選擇C。

【拓展】情態(tài)動(dòng)詞can 可表示能力、許可、可能性。如：

（1）     Some of us can use the computer now , but we couldn't ten years ago. （表能力）

（2）I thought the story could not be true（表可能性）

（3）Can/Could I go now? （表許可，常用于口語(yǔ)中）

【句意】他一直在想辦法，直到想出辦法為止，他想睡，但無(wú)法入睡。