什么是浮力？
参考答案：
浮力系根据阿基米德定理，物体入水后必排开等量的水，由于水的难以压缩特性，以体积换取等量容积得到水的支撑力是向上的，故称浮力。
This is his only request that the room_______ after being used.
A．be cleaned
B．would be cleaned
C．is cleaned
D．will be cleaned
