过去时：They went to Beijing.
They didn't go to Beijing.
现在时: They like English.
They don't like English.
一般将来时:形式一：They are going to play football.
They are going to play football.
形式二：They will play football.
They will not play football
现在进行时:They are playing football.
They are not playing football.
以上所有时态的例句中，前一句是肯定句，后一句是否定句。
