注意几种时态的区别：
(1)一般现在时：表示经常、反复发生的动作或存在的状态。
We study hard at school every day.
He goes to school by bike.
(2)一般过去时：表示在过去某个时候发生的动作或存在的状态，也表示在过去某段时间里经常发生的习惯性动作。
Did you go there last week?
I went to see my uncle yesterday.
(3)一般将来时：表示在将来会发生的动作或存在的状态。
I’ll come to see you next Sunday.
She is babysitting her sister this weekend.
We are going to Wuhan next Monday.
(4)现在进行时：表示在说话时或现阶段正在发生的动作或存在的状态。
(5)过去进行时：表示在过去某个时间正在发生的动作或存在的状态。
What was she doing when you came in?
They were watching TV when I went into the room.
(6)现在完成时：表示在说话时刚刚结束的某一动作或状态。
I have learned English for 5 years.
Have you ever been to Singapore?
(7)现在完成进行时：表示某一在过去开始，一直延续到现在，有可能刚刚结束，也有可能要继续下去的动作。
We have been skating for two hours.
She has been learning Chinese since she came to China.
注意各种时态的构成形式和不同功能。