(1) "need" 当 (main verb) 用时应该加 "to" :
(a) I think he doesn't need to worry about his health.
(b) He needs money to buy a car.
(c) He needs to work as he has a big family.
(d) He needs to go.
(e) Does he need to go so soon?
(f) He doesn't need to go.
(2) 当 (auxiliary verb) 用时不能加 "to":经常只使用 (present tense).
(a) I think he needs worry about his health.
(b) I think he needs not worry about his health.
(c) He needn't go.
(d) Need he go so soon?
(3) 助动词 auxiliary verbs = need,can,may...你好 请问这句怎么回答 I think he ______ worry about his health.上面已经给你答案了:用<助动词> (auxiliary verb):(a) I think he worry about his health. 他需要担心...或(b) I think he worry about his health. 他不需要担心...亲 可是应该是 needs to 还有needs not不行 如果是否定的话是 I don't think he needs to worry about his health.似乎从句不能否定 只能在主句里否定需要看上下文/前后关系 [context]. (c) I think he needs (to) worry about his health. 亦没错!