β源放射性核素是哪种()
A．碘-125
B．锶-90
C．铱-192
D．钴-60
E．铯-137
参考答案：B
两水池水位恒定，如图6-38所示。已知管道直径d=10cm，管长l=20m，沿程阻力系数λ=0.042，局部阻力系数：弯头ζb=0.8，阀门ζv=0.26，通过流量Q=65L/s，则水池水面高差H为（）。
A. 33.18m
B. 43.93m
C. 26.77m
D. 11.42m
--- ________it was yesterday because of the storm!
---So it was!
A．What bad weather
B．What a bad weather
C．How bad a weather
D．How bad weather
