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: Supply and demand is perhaps one of the most basic concepts of economics and it is the backbone of a market economy. Demand refers to how much of a product or service is desired by buyers. The quantity demanded is the amount of a product people are willing to buy at a certain price; the relationship between price and quantity demanded is known as the demand relationship. Supply represents how much the market can offer. The quantity supplied refers to the amount of a certain goods producers are willing to supply when receiving a certain price. The relationship between price and how much of a goods or service is supplied to the market is known as the supply relationship. Price, therefore, is a reflection of supply and demand.    The law of demand states that, if all other factors remain equal, the higher the price of a product, the fewer people will demand that product. The amount of goods that buyers purchase at a higher price is less as the price of a product goes up, so does the opportunity cost of buying that product.    Like the law of demand, the law of supply shows the quantities that will be sold at a certain price. But unlike the law of demand, the supply relationship shows an upward slope. This means that the higher the price, the higher the quantity supplied. Producers supply more at a higher price because selling a higher quantity at a higher price increases the whole income.    Now that we know the laws of supply and demand, let's turn to an example to show how supply and demand affect price.    Imagine that a CD of your favorite band is sold for $20. Because the record company's previous analysis showed that consumers will not demand CDs at a price higher than $20, only ten CDs were sold because the opportunity cost is too high for suppliers to produce more. If, however, the ten CDs are demanded by 20 people, the price will then rise. As a result, the rise in price should cause more CDs to be supplied as the supply relationship shows that the higher the price, the higher the quantity supplied. If, however, there are 30 CDs produced and demand is still at 20, the price will not be pushed up because the supply is more than the demand. 
 Question: We know from the passage that changes in the prices of product cause changes in   _  . 
 Options: (A) income and expense (B) invention and production (C) market and society (D) supply and demand

Ex Output:
D


Ex Input:
Article: When it comes to human resources, hiring highly-skilled staff is not usually enough for a company to function successfully. Besides the knowledge in their particular fields, employees must always have additional skills-----those of co-operation. In the case that work tasks can only be carried out by communicating with people, accepting common decisions, solving problems, sharing information and helping one another, teamwork skills are important. While some jobs may require talent, the ability to work as a team is learned. There are no complicated formulas ; you don't need to have any special qualities or exceptional mental abilities. Individuals can be effective as a team if they have developed certain behaviors or habits of communication. Many companies, clubs and organizations use team building activities. Team building activities may include a number of teamwork elements. They are aimed at encouraging active participation in task accomplishment while all members have their roles as individuals and are able to co-operate towards a common goal as a team. Many team building activities focus on problem solving and discussing team issues; thus argument as a way to common consensus   is encouraged. Team building activities often involve recognition and identification of team member skills, talents, knowledge, and experiences which allow the team members to learn more about each other and fully utilize   those skills where appropriate . Many team activities are focused on developing keys to trust during challenging times. 
 Question: In the author's opinion, which of the following is important for a company to be successful? 
 Options: (A) Specialized knowledge. (B) Highly-skilled staff. (C) Exceptional talent. (D) Teamwork skills.

Ex Output:
D


Ex 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

Ex Output:

D


