could have done是什么时态

例句：

Her hair could have done with a wash.

她的头发该洗一洗了。

I could have done without being woken up at three in the morning.

其实用不着在凌晨三点钟就把我叫醒。

She was away from school for 15 weeks, a handicap she could have done without

她有15周没上学，这给她带来了本不该有的障碍。

Whoever could have done such a dreadful thing?

究竟是谁能干出这种可怕的`事呢？

It was hard to visualize how it could have been done.

很难想象这是如何办到的。