. The biggest problem for most plants, which ___ just get up and run away when threatened, is that animals like to eat them.

A．shan’t

B．can’t

C．needn’t

D．mustn’t

具有润肠通便作用的药物是（）

A.党参

B.何首乌

C.熟地黄

D.枸杞子

E.冬虫夏草