收益/成本比率为3.2的意思是:()。
A、每单位美元利益为3.2美元
B、每美元利益为3.2美元
C、每单位产品利润为3.2美元
D、每单位美元利润为3.2美元
参考答案:B
—Could you please come to the museum with me this afternoon?
—Sorry, I ______. I have to take a piano lesson at 2 pm. [ ]
A. couldn't
B. mustn't
C. can't
D. needn't
对于中、长输电距离来说,特高压输电线路的输电能力主要受()的限制。