"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
