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 are also given a question about the story that requires an understanding of the relationship described in the background paragraph and the story. You need to come up with an answer to the given question; the answer will be a span from either the question or the story. In order to correctly answer the given question, you need to understand the relationship mentioned in the background paragraph and should be able to use it to understand that in the story. Your answer can not consist of any word that is not mentioned in any of these: the background paragraph, the story, or the question. You can directly copy and paste a span from the story or the question while answering the given question.

[EX Q]: Background Paragraph: Iron is first oxidized to iron(II) ions by oxygen. In the second step, the iron(II) ions are further oxidized and combine with water and oxygen gas to produce a hydrated form of iron(III) oxide known as rust. Rusting is one of many example of corrosion. Corrosion is the deterioration of metals by redox processes. Corrosion causes enormous amounts of damage to buildings, bridges, ships, cars, and other objects. It has been estimated that corrosion costs the U.S. economy over 100 billion dollars each year. A great amount of time and effort is spent to try to limit or prevent corrosion.
Story: Two neighboring cities had different climates. Dune city had very dry air and no rain, while Bay city had very high humidity, fog and lots of rain.
Question: Which city had more problems with corrosion?
[EX A]: Bay.

[EX Q]: Background Paragraph: For example, a radioactive isotope of iodine (I-131) is used in both the diagnosis and treatment of thyroid cancer. The thyroid will normally absorb some iodine to produce iodine-containing thyroid hormones. An overactive thyroid gland will absorb a larger amount of the radioactive material. If this is the case, more and more radioactive iodine can be administered, where it will cluster in the diseased portion of the thyroid tissue and kill some of the nearby cells. Cancer treatments often cause patients to feel very sick, because while the radiation treatment kills the unwanted cancer cells, it causes damage to some healthy cells in the process.
Story: John is a doctor in a local hospital. Today, he is seeing two patients, patient A and patient B. Patient A has thyroid cancer, but patient B does not have thyroid cancer. John is trying to see the difference between these two patients' reports.
Question: Which patient would risk damaging healthy cells, patient A or patient B?
[EX A]: patient A.

[EX Q]: Background Paragraph: For an inclined plane, the input distance is the length of the sloping surface, and the output distance is the maximum height of the inclined plane. This was illustrated in Figure above . Because the sloping surface is always greater than the height of the inclined plane, the ideal mechanical advantage of an inclined plane is always greater than 1. An inclined plane with a longer sloping surface relative to its height has a gentler slope. An inclined plane with a gentler slope has a greater mechanical advantage and requires less input force to move an object to a higher elevation.
Story: John works as a mechanical engineer in the auto industry. He is testing three surfaces, surface A, surface B, and surface C for their usability. Surface A has a gentler slope, surface B has a steeper slope, and surface C doesn't have any sloping. He needs to figure out advantages and disadvantages of each slope.
Question: Which surface would need less input force to move an object upward, surface A or surface B?
[EX A]:
surface A.