A pH strip is a strip which helps in determining whether a solution is acidic or basic in nature.
That is, if a solution is acidic in nature then a pH strip will change from blue to red. Whereas when a solution is basic in nature then a pH strip will change from red to blue.
Thus, we can conclude that statement molecules in the paper react differently with hydronium and hydroxide ions, best describes how a pH test strip works.
Molecules in the paper react differently with Hydronium and Hydroxide.
pH paper deals with acidity and basicity of something. You are correct in thinking that A is the answer. Always go with your gut. don't be like me when I was in college who always second guessed my answers. Good luck with chemistry.
