哪条环路是北京第一条环城高速公路( )
A．二环路
B．四环路
C．五环路
D．六环路
参考答案：C
Rick couldn't play the drums with one arm ______ a friend developed special drums for him. [ ]
A. since
B. after
C. when
D. until
何种临床操作需要实施手术室外麻醉？
