"生痰之源"指的是( )
A.肺
B.肝
C.脾
D.肾
E.心
参考答案:C
The Palace Museum is the best place _____ I've ever visited. There are many old things in it. [ ]
A. who
B. that
C. where
图8-159理想运放电路中,输出电压Uo为()。
A.2V
B.0
C.6V
D.-2V