i think (playing)is (不填）great fun谁能解释以下括号里为啥填那些而不填原形和a?

I think swimming is more dangerous than playing table tennis同义句转换I think playing table tennis is _____ _____ than swimming I think playing computer games too much is bad for us为什么这里要用is? I think playing computer games is a w______ of time,so I never play them. I think playing basketball is interesting里为什么play要加ing I think playing basketball is boring 又不是正在进行时,为什么要加ing? I think playing table tennis is interesting and A happy B fun C strong D favourite i think (playing)is (不填）great fun为什么括号里这么填? I think it is not w____ to spend hours playing football after school I think what really offends is not the winning but the playing. does sandy think playing volleyball is fun?i think i have a healthy lifestyle.这两句中第一句think 后动词加ing,第二句没有加,为什么? I think playing basketball is enjoyable.英文,变同义句I think 空 is enjoyable 空 空 basketball.英语题太难了啊! I think plauing tennis is ___ more interesting than playing chess.A.little B.farC.manyD.a few I think is show i think science is i I ______ Jack ______ playing in the garden at that time.A.think,wasn't B.don't think ,wasn'tC.don't think,was D.think ,is,这几个选项选哪个? i think he likes playing volleyball改为否定句 I think we must p__ playing football more 选择 I think ______ is _____ great fun.A.play the cards,a B.play cards,/ C.playing the car选择I think _______ is _______ great fun.A.play the cards,a B.play cards,/ C.playing the cards,a D.playing cards,/--- Where is your grandpa?--- He ______.He