七、needn't +have+-ED 分词：表示不必做的事情却做了，可译为“其实不必”。

You needn't have woken him up.It's only five. 你其实不必叫醒他，现在才 5 点。

"must +be "表示对现在所发生事情的肯定推测，如用否定句或疑问句，

应使用 "can"或 "can't"

"can be"有时表示偶尔发生的事情：

It's already half past eight.He must be waiting for us at the gate. What he has said can't be true.

Children can be very trying sometimes.孩子们有时非常讨厌。"Could"有时表示“想要”的意思（用于肯定句）：

It's so hot.I could have a dozen ices.天气真热，我真想吃一打冰淇淋。

此外，情态动词 "may"与副词 "well"连用可以表示“有足够的理由去做什么事”：

You may well tell her what happened.你尽可告诉她发生的事情。We may just as well stay wbere we are.我们留在现在的地方倒也不错。

You may just as well go as not.你去也行，不去也行。