问题补充：
There were two small rooms in the house, served as a kitchen.
A. the smaller one of which
B. the small one
C. the smaller of them
D. and the smaller one of which
答案：
(答案→)A. the smaller one of which
B. the small one
C. the smaller of them
D. and the smaller one of which
解析：句中用逗号,所以是定语从句；如果改为分号或者在空格前加and,则选the smaller of them.
