在一定情况下可以互相转换，以下是几种常见的转换形式：
1.一般过去时与现在完成时的转换
A. He joined the League two years ago.
B. He has been in the League for two years.
C. It is two years since he joined the League.
D. Two years has passed since he joined the League.
2.一般现在时与现在进行时的转换
Peter is at work，but Mike is at play.
Peter is working，but Mike is playing.
3.现在进行时与一般将来时的转换
The train is leaving soon.
The train will leave soon.
4.“be going to+动词原形”与“will(shall)+动词原形”结构的转换
We are going to visit the Great Wall next Sunday.
We shall visit the Great Wall next Sunday.
济南李大妈
