Every morning I get up at 6:00 because I have two dogs ______ at the door for me to take them out for the routine walk.

A．to wait

B．wait

C．waited

D．waiting

一长为180m的火车正以36km/h的速度匀速行驶，有一人因有急事坐汽车沿与铁轨平行的公路由列车尾部去追赶车头的司机．已知此人用了1min才追上，则汽车的平均速度为多少？