I went to the USA.一般过去时
I didn't go to the USA.一般过去时否定句
Did you go to the USA?一般过去时疑问句
I did my homework.一般过去时
Ididn't do my homework.一般过去时否定句
Did you do your homework?一般过去时疑问句
I was doing my homework.过去进行时
I wasn't doing my homework 过去进行时否定句
Were you doing your homework?过去进行时疑问句