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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: The modern world is full of useful objects that were invented by someone, from spoons and chopsticks in our kitchens to the Ipads in our handbags. Each invention is an example of the creative power of the human mind. Where do inventors get their inspirations ? The inspiration behind each of these inventions varies. Take the shopping cart as an example. Sylvan Goldman was a grocery store owner. Like most businessmen, he wished that his customers would buy more so that he could make more money. He knew what if they could carry more goods easily as they were shopping, when his sales would go up. While thinking about the problem one night, he had an idea. Working with a local handyman named Fred Young, he designed the first shopping cart. Today, retailers who use shopping carts sell more goods and make more profits. Nature has also inspired inventors throughout history. This is what happened to George de Mestral one day. While hunting with his dog in the Swiss Alps, he noticed how the burs of certain plants stuck to his clothing and to his dog' s fur. After examining them under a microscope, he found they had tiny hooks that could easily stick to the fibers of clothing or animal hide. For the next ten years, George de Mestral searched for the hest way to produce his idea. The result of his original inspiration was Velcro, which is used in many modem objects, including sportswear, shoes, automobiles, and even space suits. These examples show us that there are at least two possible inspirations for human creativity in the world of inventions -- profit and nature. No doubt, the future will continue to breathe new life into the economies of the world with fresh ideas and inventions. How many of their creations will be inspired by natural phenomena? The world's problems require creativity and we can expect best solutions from future generations.
Question: Why did sales go up in Sylvan Goldman's grocery store after he began providing shopping carts?
Options: (A) Because grocery stores without shopping carts made less money. (B) Because he lowered the prices of his goods. (C) Because customers liked the shopping cart's creative design. (D) Because customers were able to carry more items when shopping.
Solution:
D