问题补充:
---Are Mr. and Mrs. Wang living alone in the house?
---Yes, they have three sons, but of them live in their own houses.
A. neither ????
B. both
C. all
D. none
答案:
A. neither ????
B. both
C. all
(答案→)D. none
解析:根据but可知下文为否定的意思,neither表示两个都不,哦、none表示三个及三个以上都不,none指代三个儿子,选D。