5. needn’t have done
needn’t have done 表示过去做了某事，但没有做的必要， 意为“本没必要…”。
You needn’t have waken me up; I don’t have to go to work today.
注：表示推测过去某动作发生的可能性时，就表示的可能性程度而言，must最大，could其次，may更次之，might最小。例如：
“I wonder how Tom knew about your past.”
“He must / could / may / might have heard of it from Mary.”
二、情态动词 动词进行式
情态动词 行为动词进行式（即情态动词 be doing形式），表示推测或评论某动作现在是否正在进行。例如：
1）He must be playing basketball in the room.
2）She may be staying at home.
三、情态动词 动词完成进行式
情态动词 行为动词完成进行式（即情态动词 have been v-ing 形式），表示推测或评论过去某动作是否正在进行或一直在进行。例如：
1）They should have been meeting to discuss the problem.
2）He may / might have been buying stamps in the post office when you saw him.
四、某些情态动词的非凡用法
1. need
考试中主要测试 need 作情态动词与作实义动词的区别.
情态动词need与实义动词need 在时态、肯定、否定结构上的对比见下表。
时态 情态动词need 实义动词 need
现在时 He need (needn’t) do
Need he do….? He needs (doesn’t need) to do
过去时 He needed (didn’t need) to do
将来时 He need (needn’t) do
Need he do….? He will (not) need to do
注: need 一般用于否定句或疑问句.
2. dare
考试中主要测试dare作情态动词和作实义动词的区别。
情态动词dare 与实义动词dare 在时态、肯定、否定、疑问结构上的对比见下表。
句型 情态动词dare 实义动词 dare
肯定句 现在时 dare to 少用
过去时 dare to 少用 现在时 dare/dares to do
过去时 dared to do
否定句 现在时 daren’t/dare not do
过去时 dared not do 现在时 do/does not dare (to) do
过去时 did not dare (to) do
疑问句 现在时 Dare he do?
过去时 Dared he do? 现在时 Do you/Does he dear (to) do?
过去时 Did he dare (to) do