表示状态，思想，感情和感觉的动词不能表示正在进行的动作
1. 表示感觉，感官的词
see, hear, like, love, want,
2. have, has当”拥有”讲时没有进行时
3. 一般过去时
表示过去发生的动作或事件， 常和表示过去的时间状语连用，如yesterday, last night, the day before yesterday, 3 days ago,
含有be动词的句子， 将动词变为过去式，am, is的过去式为was，are的过去式为were
I was at the butcher’s.
You were a student a year ago.
The teacher was very beautiful ten years ago.
★变疑问句将be动词移动到句首
Were you at the butcher’s?
Were you a student a year ago?
Was the teacher very beautiful ten years ago?
★变否定句在be动词后面加not
I was not at the butcher’s.
You were not a student a year ago.
The teacher was not very beautiful ten years ago.
★肯定回答否定回答
Yes, I was. No, I was not.
Yes, you were. No, you were not.
Yes, he/she was. No, he/she was not.
★特殊疑问句：
What did you do?