When fire pumps are used for other than firefighting service,each pipe connecting the other service (except for branch lines used for deck washing) must have a().
A. check valve installed in the line
B. shut off valve at a manifold near the pump
C. quick disconnect union within ten feet of the pump
D. regulator in the line set at 125 psi
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碳水化合物是由()元素组成。
A. N四种元素
B. H两种
C. O三种
盾构法施工用于穿越地面障碍的给排水主干管道工程,直径一般()以上。
A. 3000mm
B. 5000mm
C. 2000mm
D. 1000mm