I think it is necessary for my 17-year-old son to have his own mobile phone ,for I sometimes want to make sure if he ------ home for dinnerA come B comes C has come D will come

I it think is right it作形式宾语——find/think/belive+形容词/名词/for sb.+to do sth.例句：we all think it necessary to do exercise.关于这个句式,为什么不是it+is+形容词/名词 即：we all think it's necessary to do exercise.此时 it's necess it is not what i think you think but what you think i think you think. I think it is very interesting 是什么意思 i think it is about dreams. I don’t think it is { } coat I think it is my worry too I think it is __________ interesting movie i think it is improssble是什么意思 but I think it is very i think it interesting为什么没有is? i think it is improssble是什么意思 I think,friendship is a________.It can___________. it is too bad.I think (),too. I think it is bad for us It is very cloudy.I think it _________（rain）. I think it impossible 还是 it is mpossible I think it is not anything is possible是什么意思?