i think It (is) useful to learn english well.括号里面的is要不要加?

I it think is right Homework Homework,every student,every day,even every night,They all need think:Did I finish my homework?Different students have different thoughts about homework.According to a survey,parts of students all thought doing homework is necessary and usef 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?