—Your sister’s plan is not quite practical.Why not try to persuade her to give i

题型：不详难度：来源：

—Your sister’s plan is not quite practical.Why not try to persuade her to give it up?
—My sister is very stubborn，so it is________to try to change her mind.

A．by chance	B．in vain
C．on purpose	D．for sure

答案

B

解析

句意为：——你妹妹的计划不是很切合实际。为何不劝她放弃？——我妹妹很固执，所以要她改变主意根本就是白费力气。in vain意为“枉费心机，白费力气”。by chance碰巧，凑巧；on purpose故意地；for sure毫无疑问。