What does it mean for a cell to have an optimal pH range?

- it will only function properly at a neutral pH of 7.
- it will only function properly on or around a specific PH that can be any value.
- it will only function when in an alkaline ( which is another word for a base) environment with a pH or 8 or above.
- it will only function when in an acidic environment with a pH at 6 or below.