I do not think he needs help.已经有do,为什么后边还是三单

I do not think he needs help.已经有do,为什么后边还是三单 i do not think he is right help 后边接动词不定式还是动词原形?有没有help sb,do sth.help sb,to do sth,help l think he needs help（便否定） Do you have a headache 否定回答 I do not think he has.为什么要用has 不用have I do not think he knows Chinese history中的know为什么加s i think he needs help改为否定句i()think he() help 是He needs to do homework还是He needs to do homework?need do 与n Tom isn't good at Maths.I think he needs to do more (things Tom isn't good at Maths.I think he needs to do more_____abou i do not think he can speak french ,_______? i do not think he told the truth,（）?