∵不含xy项,
∴-2k+12=0,
解得k=14.
故选D.
对流量相对稳定的长输管线,自动取样时宜先采用()取样。
A.时间比例
B.流量比例
C.连续
D.间歇
Wearing a seat belt saves lives;it reduces your chance of death or serious injury by more than half.