---Are Mr. and Mrs. Wang living alone in the house?-Yes they have three sons but of

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。