如果气体温度不变,体积减少,以下那个正确?PV=nRT
A.气体的质量减少
B.气体体积增加
（答案给的是B,why?我觉得很奇怪啊,A不是挺对的吗?）
If the volume of a gas is decreased while its tempreture is held constant,which of the following will occure?
A.The average kinetic energy of the molecules of the gas will increase.
B.The average kinetic energy of the molecules of the gas will decrease.
C.The mass of the gas will decrease.
D.The volume of the gas will increase.
E.The volume of the gas will decrease.