黄河上、中、下游地区具有优势的能源分别是（）
A.水能、石油、煤炭
B.石油、煤炭、水能
C.水能、煤炭、石油
D.煤炭、石油、水能
参考答案：C
— Didn't your friends play computer games yesterday?
— _________. They watched TV yesterday. [ ]
A. Yes, they didn't
B. No, they did
C. No, they didn't
D. Yes, they did.
同样负载，电源电压降低时，电机出力（）。
A、增大
B、无关
C、减小
