A:island
B:clean
C:take
D:play
(不唯一)
在下面列举的各个实例中,哪些情况机械能是守恒的?( )
某物体沿水平方向运动,其v-t图象如图所示,规定向右为正方向,下列正确的是( )
I ____(赞同) of your trying to make some money, but please don't neglect your study.