问题补充：
On the third floor there are two rooms, is used as a meeting-room.
A. one of them
B. the larger of which
C. and a larger of them
D. the largest one of which
答案：
A. one of them
(答案→)B. the larger of which
C. and a larger of them
D. the largest one of which
解析：两间房间所以用比较级不用最高级，排除D。A前加and， C中必须用the
