Fact 1: All life relies on a relatively narrow range of pH, or acidity.

Fact 2: Acidity is measured with a pH meter or with pH paper strips.

Given the two facts above, answer the question "What relies on a relatively narrow range of something you can measure with paper strips?" with the following options: 
- Length
 - voltage
 - all life
 - mammals
 - humans
 - Most plants
 - agriculture
 - animals


 

   all life      