He is reading a book now.他正在看书.
He was watching TV when his mother came in.他妈妈进来时，他正在看电视。
They've been waiting for you for three hours.他们等你三个小时了.
I'm looking forward to seeing you again.我期盼着再次见到你.
The boy is so excited about hearing from his mother.男孩为收到他妈妈的来信很兴奋。
I Practising speaking English Every day.我每天练习说英语.
Could you mind opening the door?你介意开门吗？
I have finished reading three books.我已经看完三本书.
The old man Enjoys living in the country.这老人喜欢住在农村.
We have fun Playing in the park on Sunday.
Most students have problems speaking English.
There is a boy Crying over there.
I felt something moving in the house.
I heard someone singing in the next room.
Swimming is very popular in summer.
His job is teaching English. 综上所述，动词在以上六种情况需要加ing