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.

Example input: 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
Example output: B
Example explanation: 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.
Q: Article: How would you like to brush a crocodile's teeth? Or give a shark a bath? Cats are well-known for the way they keep themselves clean by licking , but other animals have their own ways to stay clean as well. And tidiness can be important for their survival. Even cockroaches have to keep their feelers clean to help them into food. Many animals in the wild, such as deer, wolves and bears, have an automatic cleaning system. Insects like to attach themselves to animals to feed on the skin or blood. These parasites can be unhealthy. But their "host" animals are constantly dropping skin and fur by a natural process. They also like to rub up against trees or rocks to comfort themselves, and this removes additional skin and fur. Along with old fur goes the dirt and parasites living in the fur. While these animals may sometimes take a bath when they enter or cross a river or lake, they don't need the water to stay clean. They don't get sweaty, because they don't have sweat glands all over their bodies the way people do. Growing new skin and fur is enough to keep them clean. Some animals and birds use dust to get clean. Chinchillas, a kind of small animal that lives in the mountains of South America, have a very fine fur. (They are raised for their fur, in fact.) If they took water baths, they might get too cold. So, instead, they roll around in fine dust, raising quite a cloud as they "bathe". The dust helps to keep their fur and skin dry. This protects them from bacteria and parasites that enjoy warm and wet places. And the fine dust doesn't stick in their fur for long. It falls off or blows away. As for lions and tigers, their rough tongues act like combs and can remove dirt and loose fur. Why is it important for them to stay clean and smooth? It helps them stay cool in very hot summer or feel warm in cold winter.
Question: What's the main idea of this passage?
Options: (A) Animals enjoy living in a clean environment. (B) Animals fight against parasites in different ways. (C) Unlike people, animals hate staying in water. (D) For animals, cleanliness is a survival skill.
A:
D