Before joining the Department of Defense, Mr． Panetta as director of the CIA from February 2009 to June 2011．
A. would serve
B. served
C. was served
D. had been served
网友回答
A. would serve
(答案→)B. served
C. was served
D. had been served
解析：考查时态。根据本句的时间状语：from February 2009 to June 2011说明在过去的时间发生的事情，使用过去时即可。Serve没有被动语态。故B正确。