When we arrived in used to be called the foggy capital，we found London pletely changed.London is now one of the capital cities in the world with the finest air quality.
A. which
B. what
C. that
D. where
网友回答
A. which
(答案→)B. what
C. that
D. where
解析：宾语从句中缺少主语，故用what连接。