三视图中上下排列的是（）
A.主视图与左视图
B.俯视图与左视图
C.主视图与俯视图
参考答案：C
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
下列繁殖方式中属于有性生殖的是 ( )
A．柳的扦插
B．石榴的压条
C．苹果的嫁接
D．小麦依靠种子繁殖后代
