在标准状态下，体积相同的氦气和氢气，它们分子的平均动能<img src="/Image1/7c/7ca8971e585b218fed8da62f47181476.jpg" />和平均平动动能<img src="/Image1/21/2196af57968a00874aa988c8b81a3bbc.jpg" />的关系为（）。<br>A:<img src="/Image1/7c/7ca8971e585b218fed8da62f47181476.jpg" />和<img src="/Image1/21/2196af57968a00874aa988c8b81a3bbc.jpg" />都相等<br>B:<img src="/Image1/7c/7ca8971e585b218fed8da62f47181476.jpg" />相等而<img src="/Image1/21/2196af57968a00874aa988c8b81a3bbc.jpg" />不相等<br>C:相<img src="/Image1/21/2196af57968a00874aa988c8b81a3bbc.jpg" />等而<img src="/Image1/7c/7ca8971e585b218fed8da62f47181476.jpg" />不相等<br>D:<img src="/Image1/7c/7ca8971e585b218fed8da62f47181476.jpg" />和<img src="/Image1/21/2196af57968a00874aa988c8b81a3bbc.jpg" />都不相等