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: Sensing phantom phone vibrations is a strangely common experience. Around 80% of us have imagined a phone vibrating in our pockets when it's actually completely still. Almost 30% of us have also heard non-existent ringing. Are these signs of madness caused by digital culture? Not at all. In fact, phantom vibrations and ringing indicate a fundamental principle in psychology. Psychologists use a concept called Signal Detection Theory to guide their thinking about the problem of perceptual judgments. Working through the example of phone vibrations, we can see how this theory explains why they are a common and unavoidable part of healthy mental function. When your phone is in your pocket, the world is in one of two possible states: the phone is either ringing or not. You also have two possible states of mind: the judgment that the phone is ringing, or the judgment that it isn't. Obviously you'd like to match these states in the correct way. True vibrations should go with "it's ringing", and no vibrations should go with "it's not ringing". Signal detection theory calls these faithful matches a "hit" and a "correct rejection" But there are two other possible combinations: you could mismatch true vibrations with "it's not ringing" (a "miss"); or mismatch the absence of vibrations with "it's ringing" (a "false alarm"). This second kind of mismatch is what's going on when you imagine a phantom phone vibration. What does that mean in terms of your phone? We can assume that people like to notice when their phone is ringing, and that most people hate missing a call. This means their perceptual systems have adjusted their bias to a level that makes misses unlikely. The unavoidable cost is a raised likelihood of false alarms of phantom phone vibrations. The trade-off between false alarms and misses also explains why we all have to put up with fire alarms going off when there isn't a fire. It isn't that the alarms are badly designed, but rather that they are very sensible to smoke and heat and biased to avoid missing a real fire at all costs. The outcome is a rise in the number of false alarms. These are inconvenient, but nowhere near as inconvenient as burning to death in your bed or office. The alarms are designed to err on the side of caution.
Question: The writer tries to explain phantom phone vibrations_.
Options: (A) by analyzing some facts (B) by giving some examples (C) from the angle of biology (D) from the angle of psychology
Example Output: D

Example Input: Article: Abby Subark is a mother of two from Boston. "For my kids, I'm nervous. I don't know if they'll be able to achieve their American dream." She may be right. More than hard work or education, the best way to get rich in America is to be born rich. It is the case that somebody who is in the upper third of income, poor scores, in the bottom on tests when they are in eighth grade, is more likely to go to college and finish college than a poor kid with the top scores. That's what the working persons' children are up against. The Economic Policy Institute finds it would take a poor couple with 2 children 9 or 10 generations to achieve middle class status. That's about 200 years. The hallmark of American opportunity has always been the ability to do better than your parents. But compared with similar developed countries, the United States ranks fifth out of six for so-called intergenerational mobility . If you look at the mechanisms for upward mobility that were so readily available 50 years ago, they are becoming out of reach, like plentiful factory jobs with good wages and affordable education and health care. White families are twice as likely as blacks to be upwardly mobile. For most people in America today, _ If you started in the middle-income class, about 40 to 45 percent of what you are making right now is due to the fact that your parents were in the middle-income class. The rest is up to you. But for the millions of people who find themselves below the poverty line and the millions more who are the working poor, their starting point for the American dream leaves them painfully far away from the middle class.
Question: The main idea of the passage is _ .
Options: (A) How the middle class comes about in the U.S. (B) It's hard to realize the American dream for the poor. (C) Wealth and social status depend on family background. (D) Upward mobility in America is never easy.
Example Output: C

Example Input: Article: Skin - diving is a new sport today. This sport takes you into a wonderful new world. It is like a visit to the moon. When you are under water, it is easy for you to climb big rocks because you are no longer heavy .Here, under water, everything is blue and green. During the day, there is plenty of light. When fish swim nearby, you can catch them with your hands.When you have tanks of air on your back, you can stay in deep water for a long time. But you must be careful when you dive in deep water. To catch fish is one of the most interesting parts of this sport. Besides, there are more uses for skin - diving. You can clean ships without taking them out of water. You can get many things from the deep sea. Now you see that skin -diving is both useful and interesting.
Question: Skin- diving is a new sport. It can take you to _ .
Options: (A) the moon (B) a new world of land (C) the mountains (D) deep water
Example Output:
D