若(2m)3=12，则m=______．

如果一个多边形的内角和是外角和的3倍，那么这个多边形是[ ]

A．四边形

B．六边形

C．八边形

D．十边形

—Time flies! The wonderful party is over．We'll have to part.

—No need to feel blue．_________

A．A still tongue makes a wise head．

B．A single flower does not make a spring.

C．All good things come to an end．

D．All that glitters is not gold.

“山是一尊佛，佛是一座山”指的是______。

以竖直上抛的小球为例说明小球的势能和动能的转化情况。在这个例子中是否存在着能的总量保持不变？