Given the task definition and input, reply with output. You are given a background paragraph that describes one or more causal or physical relationships, such as a relationship in economics, scientific law, or nature. You need to come up with a fictional story that makes use of the concepts or the relationship described in the provided paragraph. Make sure that your story does not repeat the relation in the given paragraph (e.g., by avoiding verbatim copies of the given paragraph). Start by reading the background paragraph, and determine what relationship(s) are in the paragraph. Write a story that involves the relationship(s) that you determined are in the background paragraph. Try to use your own words as much as possible and not repeat the background paragraph. Feel free to make up places and events as long as they tie back to the background paragraph in a way that you can ask a question about.

Background Paragraph: If only 1.0 mL of 0.10 M hydrochloric acid is added to 1.0 L of pure water the pH drops drastically from 7.0 to 4.0. This is a 1000-fold increase in the acidity of the solution. For many purposes, it is desirable to have a solution which is capable of resisting such large changes in pH when relatively small amounts of acid or base are added to them. Such a solution is called a buffer. A buffer is a solution of a weak acid or a base and its salt. Both components must be present for the system to act as a buffer to resist changes in pH. Commercial buffer solutions, which have a wide variety of pH values, can be obtained.
John is a scientist in a large pharmaceutical company. He devices many useful products using his knowledge of chemistry. Today, he has four solutions in front of him, solution A, solution B, solution C, and solution D. Solution A is a buffer, but solution B is not a buffer. Solution C is acidic, but solution D is not acidic. He needs to figure out what each solution does.