离心泵启动时,出口阀门要关闭是为了()启动功率。
A.增大
B.恒定
C.稳定
D.减小
参考答案:D
His laziness makes it impossible for him to the success of the research work.[ ]
A. realize
B. undertake
C. support
D. achieve
航空货物运输中,收件人如发现货物损坏,应最迟在收到货物之日起()天内提出索赔。
A、7
B、14
C、21
D、30