a reason --->so, similar situation---> as, children love game------ many adults love(do) the first sentense can not be a reason to the second sentence. so, I think 'so do'can not be answer under this circumtance.

"as do" is the correct answer. "as do" and "so do" have the same meaning, but only "as" can answer be used in your example. In the context of your sentence, "as" serves as a conjunction, and can join the two clauses of the sentence. But in the context of your sentence, "so" would be an adverb, and cannot join the two clauses. Therefore, you would have to either write two sentences, or use a semi-colon. Examples with "so": (1) two sentences: Children just love computer games. So do many adults. (2) using semi-colon: Children just love computer games; so do many adults.

"as do" is the correct answer, yes. "as do" means "just like," or "in the same way as." It also introduces a relative clause - "so do" would need to start a new sentence.

as do