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

维持泌乳的关键是（）

A.哺乳次数

B.母亲多食油汤

C.药物

D.哺乳的姿势

E.与以上无关