be doing 一定表示正在做某事吗？

     我们表示此时此刻或目前一段时间正在发生的事情用be doing结构来完成。

例如：

1. We are doing our homework in the classroom right now. 

2. It's 10 pm, but his father is still working in his office. 

3. Tom is in the library. He is helping to put the books on the shelves. 

那么，是否所有含be doing的句子都表示正在发生的支作呢？请看下列几个例子。

1. I'm coming. 我马上就来。

2. They are arriving this afternoon. 他们今天下午到。

3. He is going to school. 他要去学校。

如果表示正在去学校的途中，则应表达为He is on his way to school.