下列多项式中，不能进行因式分解的是[ ]

A．﹣a²+b²

B．﹣a²﹣b²

C．﹣a²﹣b²+2ab

D．a²﹣3a+2

It’s generous _________ them to donate money to UNICEF. They think it important

__________ them to help poor children go to school.

A．to; for

B．for; of

C．of; to

D．of; for