Refer to the drawing of four bistable symbols (see figure below).
A temperature controller uses a bistable that turns on to actuate a warning light when the controlled temperature reaches a high setpoint.
The bistable turns off to extinguish the warning light when the temperature decreases to 5°F below the high setpoint.
Which one of the following bistable symbols indicates the characteristics of the bistable?
Share your understanding of this question with the correct explanation.