具体某事是否会发生，此用法常常可以说明人或事物的特征。 如：

Accident can happen on such rainy days.

can't do表示对现在发生的事情做否定的推测。can't have done 表示对过去发生的事情做否定的推测。如：

He can't be there now.

He can't have slept through all that noise.

4. would 和should

英语中，情态动词would 并不一定与过去的时间有关，所表示的可能性比will弱。如：

A man of good sense would not laugh in such a case.

should 表示推测时，表示确定或可能有的未来或期望。如：

It's nearly seven o'clock. Jack should be here at any moment.

─When can I come for the photos? I need them tomorrow afternoon.

─They should be ready by 12:00.

Period four Learning abut language

Teaching aims:

1. Enable Ss to recognize suffix endings on words.

2. Help Ss get used to recognizing the modal verbs as belongs to a certain group.

3. Help Ss find modals to include in their conversations.

Teaching procedures:

Step 1. Revision

Ask Ss to retell the text we've learned.

Step 2. Discovering useful words and expressions

Two of the most helpful tools in learning the English language are prefixes and suffixes. The ability to recognize suffix endings on words can help students accurately guess a word's part of speech and therefore its function in a sentence.

Step 3. Practice

1. Which of these words can become adjectives with the -ous or -al ending? Which can become nouns with the -(a)tion ending? Choose the correct ending for each word and