影响老年人药物排泄的主要脏器是（）
A.肝脏
B.肾脏
C.胃肠
D.心脏
E.大脑
参考答案：B
— Which of these digital cameras do you like best?
— ______. They are both expensive and of little use. [ ]
A. None
B. Neither
C. Nothing
D. No one
下列物质中碳元素化合价为+2价的是 [ ]
A．CO
B．C
C．CO2
D．CaCO3
