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: The example of someone having a positive experience with a drug is easy to see how drug dependence and the law of effect works. The tolerance for a drug goes up as one continues to use it after having a positive experience with a certain amount the first time.[38] It will take more and more to get that same feeling. This is when the controlled substance in an experiment would have to be modified and the experiment would really begin. The law of work for psychologist B. F. Skinner almost half a century later on the principles of operant conditioning, "a learning process by which the effect, or consequence, of a response influences the future rate of production of that response.[39]. 
Story: The Speed Squad met to discuss their experiences. They all said they always had a great experience using speed and used the same amount each time. They told how many times they used speed. Todd used it 36 times, Jesse used it 40 times, Craig used it 44 times, Alan used it 56 times, Shawn used it 69 times, Clarence used it 78 times, and Sean used it 86 times. 
Question: Who has a higher tolerance for speed: Shawn or Sean?
[EX A]: Sean.

[EX Q]: Background Paragraph: Noble gases are also used to fill the glass tubes of lighted signs like the one in the Figure below . Although noble gases are chemically nonreactive, their electrons can be energized by sending an electric current through them. When this happens, the electrons jump to a higher energy level. When the electrons return to their original energy level, they give off energy as light. Different noble gases give off light of different colors. Neon gives off reddish-orange light, like the word “Open” in the sign below. Krypton gives off violet light and xenon gives off blue light. 
Story: Bob owns a store that sells signs. He has a large selection of different signs that are for sale, and they come in all sorts of different colors. His closed sign is a reddish-orange. His open sign is a violet color, and his sale sign is blue. 
Question: Which sign in Bob's store uses Neon gas?
[EX A]: closed sign.

[EX Q]: Background Paragraph: Another obvious change that occurs during puberty is rapid growth. This is called the adolescent growth spurt . In boys, it is controlled by testosterone. The rate of growth usually starts to increase relatively early in puberty. At its peak rate, growth in height is about 10 centimeters (almost 4 inches) per year in the average male. Growth generally remains rapid for several years. Growth and development of muscles occur toward the end of the growth spurt in height. Muscles may continue to develop and gain strength after growth in height is finished. 
Story: Two researches studied adolescents during puberty. Tim studied males, while Dan studied females. 
Question: Which researcher observed that growth generally remains rapid for several years?
[EX A]:
Tim.