—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

数据独立性是指( )。

A．数据依赖于程序
B．数据库系统
C．数据库管理系统
D．数据不依赖于程序