单项选择题
All items such as steam pipes, exhaust pipes and fittings which, because of their location and operating temperature, present a hazard should be adequately lagged.That means the items should（）
A.not be put into operation too early
B.be pay adequate attention to
C.be used only when necessary
D.be coated with certain material
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相关考题
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In machinery space, the valves, pipes should be（）
A.arranged as close to each other as possible to save space
B.arranged far away from each other for convenient operation
C.be fixed or clamped to avoid vibration
D.kept easy removable as to convenient repairing work -
单项选择题
The guard, fencing or shielding for moving parts or machinery can be removed for repair only when the machinery it belongs to（）
A.stays at rest
B.is working stably
C.is worn out
D.is in good operation -
单项选择题
Before starting an engine by air, the engine must（）
A.be turned by a turning gear for at least one minute
B.be turned by a turning gear for at least two minutes
C.be turned at least one complete turn
D.be turned at least two complete turns
