顺次连接任意一个凸四边形各边的中点所得的四边形一定是[ ]

A． 梯形

B． 平行四边形

C． 矩形

D． 菱形

— What was the trouble with you the day before yesterday?

— When I practiced running, my strength _____ and I fell onto the ground.

A．gave away

B．gave in

C．gave off

D．gave out