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In this task, you're given an article, a question which often contains a blank and four options (associated with "A", "B", "C", "D"). Your task is to find the correct answer (from the given options) for the question from the given article and return one of the options from "A", "B", "C", and "D". Do not generate anything else apart from one of the following characters: "A", "B", "C", "D". There is only one correct answer for each question.

Article: Homework can put you in a bad mood , and that might actually be a good thing. Researchers from the University of Plymouth in England doubted whether mood might affect the way kids learn. To find out the answer, they did two experiments with children. The first experiment tested 30 kids. Someshapes were hidden inside a different, larger picture. The kids had to find the small shapes while sitting in a room with either cheerful or sad music playing in the background. To test their mood, the scientists asked the kids to point to one of five faces, from happy to sad. Children who listened to cheerful music tended to point to the smiley faces while the others pointed to the unhappy ones. The researchers found that sad kids took at least a second less to find the small shapes. They also found an average of three or four more shapes. In the second experiment, 61 children watched one of two scenes from a film. One scene was happy, and the other was sad. Just like in the first experiment, kids who saw the sad scene acted better compared to the others. The researchers guessed that feeling down makes people more likely to focus on a problem or difficult situation. Not all scientists agree with them, however. Other studies argued that maybe, that cheerful music in the first experiment distracted kids from finding shapes. While scientists work on finding out the answers, it still might be wise to choose when to do your tasks according to your mood. After eating a delicious ice cream, for example, write an essay.
Question: Researchers did experiments on kids in order to find out _ .
Options: (A) how they really feel when they are learning (B) whether mood affects their learning ability (C) what methods are easy for kids to learn (D) the relationship between sadness and happiness
Solution: B
Why? It is clearly mentioned in the article that to the check effect of mood on children is the main purpose of the experiment. So, B is the correct answer.

New input: Article: Vending machines are found in 16% of U.S.elementary schools, 52% of middle schools and 88% of high schools.About 22% of students in grades 1 through 12 buy food in vending machines each day--and those purchases added an average of 253 calories to their diets, according to a new study in the September issue of the Journal of School Health. Just to be clear, those were not 253 calories' worth of tofu, yogurt or carrot.The most popular vending machine items included soft drinks, candy, chips, crackers, cookies, cakes and ice cream.On the plus side , kids also bought low-fat milk, fruit juice and even fruit, the study found. But the eventual effect on kids' diets was not good.Those who bought from vending machines ate an average of 156 grams of sugar per day, compared with 146 grams for those who abstained .They also consumed less fiber, iron and vitamin B. _ Vending machine customers ate 4% less sodium than other students--an average of 3,287 milligrams per day compared with 3,436 mg for those who didn't buy from vending machines.That's probably because the extra snacks made kids too full to eat as much at mealtimes, when dishes are especially Salty.In any event, kids should eat no more than 1,200 to 1,500 mg of sodium each day, according to the Mayo Clinic.Even for adults, the government recommends a daily limit of 2,300 mg. Overall, vending machines in school appear to be a threat to children's health.The researchers calculated that all that snacking adds up to about14 extra pounds per child per school year.For some students this might be a serious contributor to weight issues.The study was based on data collected from 2,309 children nationwide for the third School Nutrition Dietary Assessment Study, which was conducted by the U.S.Department of Agriculture's Food and Nutrition Service.
Question: The students using vending machines take in less of all the following EXCEPT .
Options: (A) sugar (B) fiber (C) vitamin (D) iron
Solution:
A