把下列句子改成否定句,一般疑问句,并给肯定回答,否定回答

1.He was not in the station yesterday.
Was he in the station yesterday?
-Yes, he was./No, he wasn't.
2.I was not a student three years ago.
Was I a student three years ago?
-Yes, I was./No, I wasn't.
3.They didn't swim in the river yesterday.
Did they swim in the river yesterday?
-Yes, they did./No, they didn't.
4.He didn't buy a wallet yesterday.
Did he buy a wallet yesterday?
-Yes, he did./No, he didn't.
5.这句be动词单复数似乎有点问题,不能用“was”,应该用“were”
Li Ming and Wang Ming were not in the shop just now.
Were Li Ming and Wang Ming in the shop just now?
-Yes, they were./No,they weren't.
6.Those doctors didn't go to visit Shanghai last month .
Did those doctors go to visit Shanghai last month?
-Yes,they did./No,they didn't.