Frapping lines are fitted to lifeboat davits to（）.

A.secure the lifeboat in the davits when in the stowed position

B.bring the lifeboat close along the rali in the embarkation position

C.give the occupants a safety line when the boat is being lowered from the embarkation level

D.reduce the swinging of the lifeboat at the embarkation level

横贯我国中部的运输大动脉是（）

A．京九线

B．陇海、兰新线

C．哈大线

D．京广线