Mary John has been to China before, but they know a lot about it
A. Either, or
B. Both, and
C. Neither, nor
D. Not only, but also
网友回答
A. Either, or
B. Both, and
(答案→)C. Neither, nor
D. Not only, but also
解析：
从下文but转折可知他们懂得许多关于中国的事，可知他们都没有去过中国。neither···nor表示既不···也不，故选Ｃ。Either…or表示要么…要么；both…and 表示两者都；not only…but also表示不但…而且。