历史上，曾以北京作为京城的朝代是（　　）

A．隋、唐、元、明

B．金、元、明、清

C．宋、元、明、清

D．周、汉、元、清

What a pity! I missed meeting my friend at the airport because my car was ________ in the traffic jam. [ ]

A. broken up  

B. held up

C. kept back  

D. kept up