① Are these all ours? ____ A. It is Zhang Peng's.
② Whose is it? ____ B. Yes,it is.
③ Is this yours?____ C. Yes. they are.
如图甲所示,物体受到水平推力F的作用在粗糙水平面上做直线运动.通过力传感器和速度传感器监测到推力F、物体速度v随时间t变化的规律如图乙所示.(g=10m/s2)则( )
下列旅游活动属于现代旅游的是( )