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be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?（必背）
不含有be动词的句子，将动词变为过去式：
I finished my homework yesterday.
The boy went to a restaurant.
The Sawyers lived at King Street a year ago.
★变疑问句在句首加did，动词变为原型
Did you finish your homework yesterday?
Did the boy go to a restaurant?
Did the Sawyers live at King Street a year ago?
★变否定句在主语和动词之间加did not
I did not finish my homework yesterday.
The boy did not go to a restaurant.
The Sawyers did not live at King Street a year ago.
★肯定回答及否定回答
Yes, I did. / No, I didn't.
Yes, he did. / No, he didn't.
Yes, they did. / No, they did not.