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.

Ex Input:
Article: Recent research has claimed that an excess of positive ions in the air can have an ill effect on people's physical or psychological health. What are positive ions? Well, the air is full of ions, electrically charged particles, and generally there is a rough balance between the positive and the negative charged. But sometimes this balance becomes disturbed and a larger proportion of positive ions are found. This happens naturally before thunderstorm, earthquakes when winds are blowing in certain countries. Or it can be caused by a build-up of static electricity indoors from carpets or clothing, or from TV sets, duplicators or computer display screens. When a large number of positive ions are present in the air many people experience unpleasant effects such as headaches, fatigue , excessive anger, and some particularly sensitive people feel sick or even suffer mental disturbance. Animals are also affected, particularly before earthquakes, snakes have been observed to come out, rats to flee from their burrows, dogs howl and cats jump about unaccountably. This has led the US Geographical Survey to fund a network of volunteers to watch animals in an effort to foresee such disasters before they hit vulnerable areas such as California. Conversely, when large numbers of negative ions are present, then people have a feeling of well-being. Natural conditions that produce these large amounts are near the sea, close to waterfalls or fountains, or in any place where water is sprayed, or forms a spray. This probably accounts for the beneficial effect of a holiday by the sea, or in the mountains with streams or waterfalls. To increase the supply of negative ions indoors, some scientists recommend the use of ionisers. They claim that ionisers not only clean and refresh the air but also improve the health of people sensitive to excess positive ions. Of course, there are the detractors, other scientists, who dismiss such claims and are skeptical about negative/positive ion research. Therefore people can only make up their own minds by observing the effects on themselves, or on others, of a negative rich or poor environment. After all it is debatable whether depending on seismic readings to anticipate earthquakes is more effective than watching the cat.
Question: What is an ion according to the passage?
Options: (A) It's a charged particle. (B) It's basically static electricity indoors. (C) It's a balance between the positive and negative charged. (D) It's an ill effect on people's physical and psychological health.

Ex Output:
A

Ex Input:
Article: Harvard University in the United States has been ranked as the university with the best "reputation" in the world. The Times Higher Education magazine has listed 200 top universities all over the world based on how they are regarded by a group of international college teachers. That is to say the list measures how universities are regarded, rather than how they actually performed. A subjective, word-of-mouth quality such as "reputation" has genuine economic value for universities, said Simon Marginson, professor of higher education at the University of Melbourne in Australia. "Reputation is not just an impression, though it might be not as reliable as performance by objective indicators ," said Prof Marginson. Based on the views of 13,000 college teachers around the world, it confirms the power of the big US universities, which _ this list. Seven of the top 10 are US universities, headed by Harvard and Massachusetts Institute of Technology (MIT). Furthermore, 14 of the top 20 are from the US. Cambridge is the highest ranking UK university in the list, in third place, with Oxford ranked as sixth. For students applying to university, reputation might be hard to quantify, but was an important part of the attractiveness, said the president of Cambridge University's students' union, Rahul Mansigani. "Reputation makes a huge difference. If there is an idea that somewhere is great, it will get lots of good people applying whether it's true or not. Factors such as a sense of history and the presence of outstanding college teachers were part of the reputation of Cambridge," he said.
Question: What can be inferred from the text?
Options: (A) No Asian universities are among the Top 10. (B) At least five UK universities are among Top 20. (C) The Times Higher Education magazine is from the US. (D) Reputation affects students' decisions when choosing universities.

Ex Output:
D

Ex Input:
Article: We've all heard about the power of positive thinking, but a recent study found that people who think they're getting fit actually get more positive benefits from activity, according to a Reuters Health article. The study examined hotel housekeepers over a period of four weeks. Some of the housekeepers were told that their work duties gave them enough activity to meet the Surgeon General's health guidelines . Another group of housekeepers were told nothing. After four weeks, the housekeepers who believed their work activity counted as exercise lost weight and body fat, and their blood pressure went down. The results of this study suggest that it's important to understand and believe in the positive benefits of your activity. So here are a few things to think about the next time you exercise: Just thirty minutes of quick walking each day can greatly reduce your risk of a heart attack. Even your housework -- like yard work and house cleaning -- can help you burn calories and increase your fitness levels. Weight bearing activity just a few times a week can build bone density and reduce your chances of developing osteoporosis . Three 10-minute workouts throughout the day are just as good to your health as one long workout. Moderate amounts of exercise have been linked to lower rates of heart disease, stroke and even cancer. Strength training can help make daily activities like carrying bags or laundry feel easier. Regular exercise will reduce stress, keep you in a good mood and improve the quality of your sleep.
Question: The main purpose of this passage is to _ .
Options: (A) encourage people to think they will get fit in different activities (B) tell people how to finish the work duties better (C) tell people how to lose weight (D) advise people to do more housework

Ex Output:
A