The water level in a water storage tank is being controlled by an automatic bistable level controller.
If water level increases to 70 percent, the controller bistable turns on to open a tank drain valve.
When water level decreases to 60 percent, the controller bistable turns off to close the drain valve.
Which one of the following bistable symbols indicates the characteristics of the bistable used in the level controller?
Share your understanding of this question with the correct explanation.