When the girl learnt that her boy friend was ____ in the earthquake, she _____.

A．injured; burst in tear

B．killing; burst into tears

C．still alive; burst into tears

D．missing; burst into laughter

营养干预中的类实验设计，不是因为______而为的。

A．人群没法随机分配
B．人力不足
C．实施过程未设计同期对照
D．不能开展平行随机对照试验