—Why can your neighbor know so much about London?

—He ____ have been there before.

A．must

B．can

C．should

D．need

儿童出现生长发育迟缓、消瘦、体重过轻、智力发育障碍，最可能的原因是

A．热能不足

B．蛋白质—能量营养不良

C．脂肪摄人不足

D．锌缺乏

E．钙缺乏