20.可調式減壓閥(adjustable reducing valve)通常與何種流量計合併使用？
(A)流量限制式(flow restrictor)
(B)巴頓式(Bourdon gauge)
(C)代償式索普管(compensated Thorpe tube)
(D)非代償式索普管(uncompensated Thorpe tube)

Egan's 12ed p.899 可調...