1．You shouldn't/oughtn't to have helped(help) him, because he could do it by himself.
2．Wang Lin went home. He must have finished(finish) his work.
3．Mike can't have found(find) his bike, for he came to school by bus this morning.
4．I needn't have bought(buy) so much wine—only five people came.
5．Today is Sunday.You needn't have come(come) to school.
Ⅱ.翻译下列句子，观察划线部分并归纳写出句子所包含的结构和用法
1．This pen must be yours.
这肯定是你的钢笔。must＋动词原形，表示对现在情况的肯定推测。
2．He must have been to Beijing, for he knows it very well.
他肯定去过北京，因为他对北京非常熟悉。must have＋过去分词，表示对过去情况的肯定推测。
3．This cannot be done by him.
这件事不可能是他做的。cannot＋动词原形，表示对现在情况的否定推测。
4．He cannot have been to the city.
他不可能去过那个城市。cannot have＋过去分词，表示对过去情况的否定推测。
5．He may be very busy now.
他现在可能很忙。may＋动词原形，表示对现在情况的不太肯定的推测。
6．He may not have finished his homework.
他或许还没有完成他的作业。may not have＋过去分词，表示对过去发生的情况的不太肯定的推测。
