当调压器进口压力（）中间压力，但又大于低压额定压力时，主阀敞开，指挥系统失效，中压直通低压。
A.大于等于
B.小于等于
C.大于
D.小于
参考答案：D
硬膜下间隙阻滞的临床特点有（）
A.通常产生广泛阻滞
B.与全脊麻一样迅速严重
C.小量麻药即产生广泛阻滞
D.血压变化不大
E.可能无引起硬膜外广泛阻滞的诱因
The official number of a documented vessel is（）.
A.not required to be anywhere on the vessel
B.required to be permanently marked on the vessel's structure
C.required to be painted on the vessel;s stern
D.required to be painted on the vessel's bow
