Most of the teaching equipment presented by the Hope Project, as well as the books,          made

good use of in the village school.[ ]

A. has    

B. have

C. have been

D. has been

一物体沿斜面匀速下滑，物体的（　　）

A．动能增加，势能减少

B．动能、势能都减少

C．动能不变，势能减少

D．机械能总量保持不变