You are presented with the quiz "What relies on a relatively narrow range of something you can measure with paper strips?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "all life relies on a relatively narrow range of pH, or acidity" and "acidity is measured with a pH meter or with pH paper strips". 

So, what's the best answer to the question?


 

   all life        