I have arranged for a car to ____________at the station.
A:pick them up
B:pick up them
C:pick them on
D:pick on them
阅读以下有关“空气成分”的卡通图,填空:
More and more parks ________in Mentougou in five years.
以卵击石,石头没有损伤而鸡蛋破了,这一现象中,石头对鸡蛋的作用力大小与鸡蛋对石头的力相比较 ( )