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
网友回答
B解析思路分析：can't表示事物本身所不具备的能力，符合句意。shan't表示“不会去做某事”，needn't表示“不必做某事”，mustn't表示“一定不要做某事”。
【点评】此题考查情态动词，难度适中。解答此类题目应掌握各种情态动词的基本含义及用法。