The correct answer is: B. equal to
The electrolyte level in a cell should be equal to the level of the plates. This is because the electrolyte helps to conduct electricity between the plates, and if the level is too low, it will not be able to do this effectively. If the level is too high, it can cause the cell to overheat and damage the battery.
Option A is incorrect because the electrolyte level should not be below the level of the plates. This is because the electrolyte helps to conduct electricity between the plates, and if the level is too low, it will not be able to do this effectively.
Option C is incorrect because the electrolyte level should not be above the level of the plates. This is because the electrolyte can cause the cell to overheat and damage the battery.
Option D is incorrect because the electrolyte level should be equal to the level of the plates.