609　should用法难点

① should用作助动词，为shall的过去式，用来构成过去将来时，主要用于宾语从句中的第一人称。

I told her that I should see her the next day. 我告诉她我将在第二天见她。

We thought we should never come here again. 我们原以为永远也不会再到这里来了。

② should作情态动词，表示“应该，应当”，通用于各种人称。

We should help each other. 我们应该相互帮助。

You should write a letter to her. 你应该给她写一封信。

Theory should be combined with practice. 理论应同实践相结合。

③ should用于第一人称，表示委婉语气，为客气、礼貌的说法。

I should say you'd better learn another foreign language. 我倒觉得你最好再学一门外语。

We should like to do the experiment right now. 我们倒是想立即做这项实验。

④ should可用于特殊疑问句中，表示意外、惊奇、不能理解等，有“竟会，竟然会，怎么会”等义。

How should I know？我怎么会知道呢？

Why should I do it？为什么要我做那件事呢？

A：Go and cut down the tree. 去把那棵树砍掉。

B：Why should I？为什么（要）我砍呢？

⑤ should be doing sth.表示应该在做什么。

You shouldn't be sitting here doing nothing. 你不应该坐在这里什么也不干。

You shouldn't be staying up so late. 你不该睡这么晚。

⑥ should have done sth.表示该做而实际未做，含有责备、遗憾、建议、指正的意味，意为“本应该”。

You should have come earlier. 你本该早些来的。

These manuscripts should have been kept in a dry place. 这些手稿本应存放在干燥的地方。

You should have told him you don't like to do it. 你来应告诉他你不喜欢做那件事的。

There is no reason why he should have sold the house. 他竟然把房子卖了，简直毫无理由。

⑦ shouldn't have done sth.表示不该做却做了，或该做却没做，含有责备等意味。

This kind of flower should not have been watered so often. 这种花本不该浇水这样勤的。

She shouldn't have left home without a word. 她不该什么也没说就离开了家。

You shouldn't have told her the news. 你本不该把消息告诉她的。（但却告诉了）

You should have told her the news. 你本该把消息告诉她的。（但却没告诉）

⑧ should用在虚拟语气中，相当于would。

If we had planted this kind of trees in a damp place，they should have grown better. 这种树要是种在潮湿的地方，会长得更好。

If I were to do the job，I should do it in a different way. 要是我来做这项工作，我会以不同的方式做。