More has been learned about the Moon than any other of the Earth's neighbors in space because of the Apollo program, which enabled men to walk on the Moon and bring back hundreds of pounds of________.

A．rocks

B．rock

C．stone

D．stones

管理方格图中用横轴表示（）

A.对民主的依赖度

B.对专制的依赖度

C.对事的关心度

D.对人的关心度