英语,就是不明白什么时候加ing!

题目

英语,就是不明白什么时候加ing!
虽然说Ing是现在进行时,可是有很多句子不是现在进行时也加了,有些句子是现在进行时却没加,谁能给我透透彻彻的讲明白.白话一点.
There is no charge for borrowing a book from the library; 这个句子为什么加
Look at the pretty lady .这个是进行时为什么不加,she's looking at the picture on the wall .w为什么加.明明都是现在进行时.

答案

V-ing并非都是表示选择进行时态,请看我下面的简单分类
现在进行时 am/is/are doing He is playing now
过去进行时 was/were doing He was playing football yesterday
介词之后 for/with/in/on + doing This book is for reading
固定词组 spend...doing We spent four days making this.
动名词 I would appreciate your calling back this afternoon.
V-ing 短语作主语 Listening to music is my favorite
V-ing 作伴随状语 He left alone,taking his luggages.