氧在血液中运输方式主要是（）。

A.与血红蛋白结合

B.物理溶解在血浆中

C.结合成碳酸氢盐

D.与碳氧血红蛋白结合

E.以上都是

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