You are given a background paragraph that describes one or more causal or qualitative relationships such as a relationship in economics or a scientific law and a story that makes use of the concepts or the relationship described in the provided paragraph. You need to come up with a question about the story that requires an understanding of the relationship described in the background paragraph. The generated question should not be answerable without both the background and story. Write a question about the story that requires a relationship in the background paragraph to answer. Check whether your question requires both the background paragraph and the story to answer. If your question can be answered by only one of these, try to rewrite your question so that it requires both. Note that "flipping" a word in the question can give rise to a new question where the answer will be different from the original question. Often, "flipping" a word gives rise to flipping the direction of the relationship, for example, from "increase" to "decrease."

[Q]: Background Paragraph: If a solution has a higher concentration of hydronium ions than pure water, it has a pH lower than 7. A solution with a pH lower than 7 is called an acid . As the hydronium ion concentration increases, the pH value decreases. Therefore, the more acidic a solution is, the lower its pH value is. Did you ever taste vinegar? Like other acids, it tastes sour. Stronger acids can be harmful to organisms. For example, stomach acid would eat through the stomach if it were not lined with a layer of mucus. Strong acids can also damage materials, even hard materials such as glass. 
Story: In his chemistry lab David is learning about acids. He took three solutions to identify them correctly, sample A, sample B, and sample C. Sample A is a strong acid; sample B is a weak acid; and sample C is not an acid. David needs to identify the content of each sample by learning about their attributes.
[A]: Which sample would have higher concentration of hydronium ions, sample A or sample B?


[Q]: Background Paragraph: Conifers have many uses. They are important sources of lumber and are also used to make paper. Resins, the sticky substance you might see oozing out of a wound on a pine tree, are collected from conifers to make a variety of products, such as the solvent turpentine and the rosin used by musicians and baseball players. The sticky rosin improves the pitcher’s hold on the ball or increases the friction between the bow and the strings to help create music from a violin or other stringed instrument. 
Story: Two neighboring towns, Pine town and Willow town, used different types of woods for lumber et al. Willow town used hardwoods, while Pine town used softwoods.
[A]: Which town used fewer conifers for lumber?


[Q]: Background Paragraph: Each radioactive isotope has a characteristic decay time period—the half-life—that is determined by the amount of time needed for half of a sample to decay. This is an exponential decay process that steadily decreases the proportion of the remaining isotope by 50% every half-life. Hence after two half-lives have passed only 25% of the isotope is present, and so forth. 
Story: David was working in his chemistry lab. He selected two isotopes, sample A and sample B. Sample A had longer half-life, but sample B had shorter half-life. After some time he checked sample A when its one half-life had passed. He noted it as sample A1. Then he came back to see it again when two half-lives had passed. He noted it as sample A2.
[A]:
After certain time, which sample would have less isotopes, sample A or sample B?