X签证(学习签证)有没有标明在华停留期限?()
A.有
B.没有
参考答案:B
The Wangs are considering ______ to Huangshan for a trip at five tomorrow morning.
A.to move off
B.moving
C.moving off
D.movement
滑雪运动员不借助雪杖,由静止从山坡以加速度a1匀加速滑下,测得20s的速度为20m/s,50s到达坡底,又沿水平面以加速度a2减速20s停止,求:
(1)a1和a2
(2)到达坡底后6s末的速度.