should和could都是情态动词,后接动词原形,没有人称和数的变化,它们的否定形式为shouldn’t和couldn’t。下面我们一起看看它们的“情态观”吧。
　　
　　一、提出建议
　　
　　should意为“应该”。用于表示义务或提出建议或要求;could意为“能够”,也可用来提出建议。如:
　　 1. We should wait a little more. 我们应该再等一会儿。
　　 2. You shouldn’t talk loudly in the library. 你不应该在图书室大声说话。
　　 3. ——What could I do to improve my English? 我怎样才能够提高我的英语水平?
　　 ——Well, you should try to speak more. 你应该尽可能多说。
　　
　　二、征求意见
　　
　　should也可用于征求意见,此时一般用于第一人称疑问句中;could用于请求或请求允许,带有一些试探性,因而显得更加委婉。如:
　　 1. Should I open the window? 我可以开窗户吗?
　　 2. What should I do for you? 我应该为你做些什么?
　　 3. Could I borrow some money from you? 我可以向你借些钱吗?
　　
　　三、推测情况
　　
　　should用来表示有较大可能性实现的猜测,意为“可能;总该……吧”;could表示推测时,意为“可能的,但又未必可能”。如:
　　 1. They should be here by now. 他们现在可能到了。
　　 2. The dictionary should be in the reading-room. 那本字典可能在图书馆。
　　 3. One day I could become a millionaire, but the chances are very small.
　　有一天我也许会成为百万富翁,但这种可能性很小。
　　【即学即练】
　　一、选择填空。
　　 1. Excuse me, can you tell me ____ next?
　　 A. how to do B. what should we do C. what we should do D. how we should do
　　 2. Maybe you ____ say sorry to her.
　　 A. must B. shall C. should D. ought
　　 3. Mrs White ____ in the office now. I saw her just now.
　　 A. should be B. shall be C. should is D. maybe
　　 4. Yesterday I gave my uncle a call to tell him that I ____ leave Beijing for London the next month.
　　 A. shall B. will C. should D. could
　　 5. An Englishman who ____ not speak Italian was once traveling in Italy.
　　 A. must B. could C. may D. might
　　 6. ——Do you still remember when we went to the Great Wall?
　　 ——I can’t remember it well, but ____ it have been someti