A、  B、  C、  B所给出的问题是一个询问John是不是来自旧金山的反义疑问句。问题最后的is he?是对前面所提出问题的确认，没有什么具体的含义，不要在这点上费心。因为问题是询问有关John的，所以选项(A)的回答I，

I wonder how long it’ll take to drive to the conference center from the airport.
(A) It depends on traffic.
(B) Because it’s close to the hotel.
(C) The flight’s just under two hours.

John’s not from San Francisco, is he?
(A) Once, with my parents when I was six, but I don’t really remember it very well.
(B) No, but he lived there for a couple of years.
(C) He’ll be there for the whole week.