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【单选题】第二篇 Sleep We all know that the normal human daily cycle of activity is of some 7 - 8 hours’ sleep alternating with some 16 - 17 hours’ wakefulness and that, broadly speaking, the sleep n...
A.
people hate the inconvenience of working on night shifts.
B.
your life is disturbed by changing from day to night routines and back.
C.
not all industries work at the same hours.
D.
it is difficult to find a corps of good night workers.
【单选题】(2012年)已知设计水文条件下排污河段排放口断面径污比为4.0，排放口上游氨氮背景浓度为0.5mg/L，排放口氨氮排放量为86.4kg/d，平均排放浓度10mg/L,则排放口断面完全混合后氨氮的平均浓度为()
A.
5.25 mg/L
B.
3.00 mg/L
C.
2.50 mg/L
D.
2.40 mg/L