单项选择题
When stand-by engine instructions have been received, it’s necessary to make it sure that all valves in the various systems are（）
A.operational
B.open
C.closed securely
D.at middle position
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相关考题
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单项选择题
The monitoring function may serve all of the following purposes except（）
A.instigating corrective action
B.indicating values of controlled variables
C.warning of off-limit conditions
D.providing record of performance -
单项选择题
A feedback is an input（）
A.which governs the state of a variable
B.which provides a visual and audible alarm
C.which indicates values of controlled variables
D.which measures the state of the controlled variable -
单项选择题
The closed-loop system differs from the open-loop system by（）
A.the lack of a feedback
B.the presence of a feed back
C.the lack of a computer
D.the presence of a computer
