问题补充：
Liu Xuan is really ,she is very good at math, physics and chemistry.
A. outgoing
B. smart
C. athletic
D. quiet
答案：
A. outgoing
(答案→)B. smart
C. athletic
D. quiet
解析：句意：刘璇真的很聪明，他擅长数学，物理和化学。A. outgoing外向的B. smart
聪明的 C. athletic 强健的D. quiet安静的
根据句意故选B.
