Final answer:
Blood is the substance closest to neutral on the pH scale.
Step-by-step explanation:
The substance closest to neutral on the pH scale is blood. The pH scale measures the acidity or alkalinity of a substance, with a range from 0 to 14. A pH of 7 is considered neutral, and blood has a pH around 7.4. Lemon juice has a pH around 2, bleach has a pH around 12, and baking soda has a pH around 9.
Learn more about The pH scale and neutrality