Look, so many passengers _________ with their smart phones on the underground.
A:played
B:will play
C:are playing
D:have played
向CuCl2溶液中加入一定量的铁粉,充分反应后过滤,得滤液和滤渣.取滤渣少许,向其中加入足量稀盐酸,滤渣部分溶解,有无色气体产生.根据上述实验作出的下列推断不正确的是( )
如图所示,在地面上以速度v0抛出质量为m的物体,抛出后物体落到比地面低h的海平面上.若以地面为零势能面且不计空气阻力,则( )