分类：教育/科学-升学入学-中考
问题：在什么情况下动词变为ing? 
回答：同意楼上的归纳"1.某些词语的固定用法。如：enjoy,finish,feel like,practise,mind,allow等，这些词后面要用动词的ing形式。
   enjoy playing football

2.现在进行时态，过去进行时
He is sleeping.  She was watching TV at five yesterday.

3.介词后
I will go to bed after finishing my homework
4.做定语
a swimming pool(a pool for swimming)
5做状语
He is sitting on the chair ,reading a newspaper "

还补充一点:6.做主语时,在动词之后加ing,变为动名词.
Reading novels is her favorite habit.