A.只有机械能守恒
B.只有动量守恒
C.只有对转轴O的角动量守恒
D.机械能、动量和角动量守恒
[单选题]A.To prove their popularity around the world.B.To reveal the public’s fear
[单选题]A.programsB.expertsC.devicesD.creatures
[单选题]A.programsB.expertsC.devicesD.creatures
[单选题]A.To prove their popularity around the world.B.To reveal the public’s fear
[单选题]A.状态aB.状态bC.状态cD.状态d