1. 现在
   1. 一般现在时
      1. do/does
         1. It seldom snows here.
   2. 现在进行时
      1. be doing
         1. He is doing well in his lessons.
   3. 现在完成时
      1. have/has done
         1. The old man has lived here for more than twenty years.
   4. 现在完成进行时
      1. have/has been doing
         1. The children have been watching TV since six o'clock.
2. 过去
   1. 一般过去时
      1. did/was/were
         1. She often came to help us in those days.
   2. 过去进行时
      1. was/were doing
         1. They were building a dam last spring.
   3. 过去完成时
      1. had done
         1. As soon as we got to the station，the train had left.
   4. 过去完成进行时
      1. had been doing
         1. He had been working all day.
3. 将来
   1. 一般将来时
      1. will do/be going to do
         1. It is going to rain.
   2. 将来进行时
      1. will be doing
         1. The train will be leaving in a second.
   3. 将来完成时
      1. will have done
         1. Before long，he will have forgotten all about the matter
   4. 将来完成进行时
      1. shall/will have been doing
         1. By the time Pierce comes back from the meeting，we will have waited here for three hours