我們表示此時此刻或目前一段時間正在發(fā)生的事情用be doing結構來完成。

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的句子都表示正在發(fā)生的支作呢？請看下列幾個例子。

1. I'm coming. 我馬上就來。

2. They are arriving this afternoon. 他們今天下午到。

3. He is going to school. 他要去學校。

如果表示正在去學校的途中，則應表達為He is on his way to school.