Barack Obama delivered a speech to 500 local youths during his visit to China，many of were from Fudan University and Tongji University．
A. them
B. whom
C. which
D. those
网友回答
A. them
(答案→)B. whom
C. which
D. those
解析：考查定语从句。Whom指代先行词500 local youths，在定语从句里作为of的宾语。句意：奥巴马在访问中国期间给500名当地的年轻人发表了演讲，其中很多人都是来自复旦大学和清华大学。