The biggest problem for most plants which just get up and run away when threatened is t

问题补充：

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

答案：

A. shan’t

(答案→)B. can’t

C. needn’t

D. mustn’t

解析：句意：对大多数植物来说，当受到威胁时竟不能站起来并逃走，因此，经常会被动物吃掉是他们面临的最严重问题。显然，B项正确。