I think he is at home.改为否定句.为什么一定要改成I don't think he is at home而不能改成I think he isn't at home?

The boy is o––– at the moment,I think he is ill again. I think he is at home.改为否定句.为什么一定要改成I don't think he is at home而不能改成I think he isn't at home? I think maybe he's at school I think he is at home now (改为否定句） 反义疑问句填空I don‘t think he is at home,______? 动词填空： -Your father is at home. -I _ (think) he was still in Beijing. I think maybe he is not at school 的同义句 I don't think he is at home ____ ____ ____(现在)-.- the or this? don't think he can ___ at school now.98.I don't think he can ___ at school now.A.areB.beC.is选那个? 他将在6点回家为什么是“he will be hom at six 而不是“he will go hom at six I think c___ is at school today. i think she is ---at English i don't think he makes many mistakes.--if at allwhat is the meaning of if at all I think he is sure to___(succeed). i donot think he who is right I think he is must abolish. Tom _____ at hom ,but I'm not sure. I'm not sure of that ,And I think he is probably at home .此句中的that