Thebiggestproblemformostplants,which

问题详情：

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

A. shall not              B. can't

C. needn't                D. mustn't

【回答】

B

知识点：虚拟语气与情态动词

题型：选择题