動詞ing
動詞ing有以下幾種情況：1.動詞加ing做謂語；2.動詞作介詞的賓語要加ing；3.部分動詞用動詞做賓語；4.一些固定句式後面要加動詞ing等。
一、動詞加ing做謂語情況
做謂語時動詞加ing前面必須加上be動詞，形成be+動詞ing(現在分詞)作句子謂語，構成進行時態句子。
例如:
He is reading a book now.
他正在看書.
He was watching TV when his mother came in.
他媽媽進來時，他正在看電視。
They've been waiting for you for three hours.
他們等你三個小時了。
二、動詞加ing做非謂語情況
1、動詞作介詞的賓語要加ing(動名詞)
I'm looking forward to seeing you again.
我期盼着再次見到你。
The boy is so excited about hearing from his mother.
男孩收到媽媽的來信，很興奮。
2、部分動詞用動詞做賓語。做賓語的動詞要加ing(動名詞)
I practising speaking English every day.
我每天練習說英語。
Would you mind opening the door?
你介意開門嗎？
I have finished reading three books.
我已經看完三本書。
The old man enjoys living in the country.
這老人喜歡住在農村。
3、一些固定句式後面要加動詞ing(現在分詞)
We have fun playing in the park on Sunday.
週日我們在公園玩得很開心。
Most students have problems speaking English.
大多數學生的英語口語都存在問題。
4、動詞修飾名詞做後置定語時，要加ing(現在分詞)
There is a boy crying over there.
那兒有一個男孩在哭。
I heard someone singing in the next room.
我聽到隔壁房間有人唱歌。
5、動詞做主語和表語時，動詞要加ing(動名詞)
Swimming is very popular in summer.
夏天人們喜歡游泳。
His job is teaching English.
他的工作是教英語。
綜上所述，動詞在以上六種情況需要加ing
