* pH Scale: The pH scale measures the acidity or alkalinity of a solution.

* 0 to 6.9 is acidic

* 7 is neutral

* 7.1 to 14 is alkaline (basic)

* Ammonia (NH₃): Ammonia is a weak base. When dissolved in water, it forms ammonium hydroxide (NH₄OH), which releases hydroxide ions (OH⁻) making the solution basic (higher pH).

* Battery Acid (Sulfuric Acid, H₂SO₄): Battery acid is very acidic (low pH).

* Isopropyl Alcohol (C₃H₈O): Isopropyl alcohol is slightly acidic, but its pH is close to neutral.

* Water (H₂O): Pure water has a neutral pH of 7.

Therefore, ammonia has the highest pH out of the listed substances.