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（）
单项选择题 The closed-loop system differs from the open-loop system by（）
单项选择题 From the passage, we can learn that the simplest controller action is（）
