1.My father bought a computer last year.
否定句：My father didn't buy a computer last year.
一般疑问句：Did your father buy a computer last year?
肯定回答：Yes,he did.
否定回答：No,he didn't.
2.I am practing my English.
否定句：I'm not practicing my Engish.
一般疑问句：Are you practicing your English?
肯定回答：Yes,I am.
否定回答：No,I'm not.
3.We took a taxi to Shanghai yesterday.
否定句：We didn't take a taxi to Shanghai yesterday.
一般疑问句：Did you take a taxi to Shanghai yesterday?
肯定回答：Yes,we did.
否定回答：No,we didn't.