52. _____ I went to the hospital to see Jack, who had _____ had an operation.

A．Just now; just now

B．Just now; just

C．Just; just

D．Just; Just now

有一恒定出流的薄壁小孔口如图示，作用水头H₀=4m，孔口直径d=2cm，则其出流量Q为（）。

A．1.82×10^-3m³/s

B．1.63×10^-3m³/s

C．1.54×10^-3m³/s

D．1.72×10^-3m³/s