All around them was only the white snow and the night; they were ____________ from the rest of the world and were conscious only of each other.

A．cut out

B．cut down

C．cut off

D．cut in

商品与空气中的氧或其他能放出氧的物质接触，所发生与氧结合的化学变化称为（）。

A.融化

B.氧化

C.风化

D.挥发