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 Q]: 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 A]: D

[EX Q]: Article: Astronaut Mark Kelly announced today that he is retiring from NASA in order to focus on the recovery of his wife, Gabrielle Giffords. Kelly, who is 47, began his NASA career in 1996. He has traveled to the International Space Station four times and served aboard space shuttles Endeavour and Discovery. Most recently he was commander of Endeavour's final voyage, which ended on June l. "After 25 years of service to our country, I am retiring from the United States Navy and leaving NASA. My retirement will take effect on October l. " he said. "This was no easy decision. Words cannot express my deep gratitude for the opportunities I have been given to serve our great nation. And I have always been proud to be a member of the NASA. Public service has been more than a job for me and for my family. My brother continues to serve in NASA and in the Navy. My parents are retired police officers. And my wife Gabrielle proudly serves in the US House of Representatives." he continued. "As life takes unexpected turns we frequently come to a crossroads. I am at this point today. Gabrielle is working hard every day on her way to recovery. I want to be by her side. Stepping aside from my work in the Navy and at NASA will allow me to be with her and with my two daughters. I love them all very much and there is no doubt that we will move forward together. After some time off, I will look for new opportunities and I'm hopeful that one day I will again serve our country." Kelly said. On Jan 8, Giffords was shot in the head and was severely injured while meeting with her supporters. She returned to her Tucson home last week for the first time since then.
Question: Mark Kelly must have been_when he announced his decision.
Options: (A) regretful (B) cheerful (C) peaceful (D) meaningful
[EX A]: A

[EX Q]: Article: World Future Society People People may live for up to 120 years and use new technology to help when people go blind, deaf and have other problems. The number of people over a hundred years old could go from 135,000 today to 2.2 million people by 2050. By 2015 people think that 100 million workers will be able to work from home for a company in a different country by using the Internet. Money Worldwide e-business will become even more successful with online shops that sell special products for each person, which will be brought to their house the next day. Environment The technology for making energy from wind and the Sun is growing very quickly. In the future wind and Sun energy could become much cheaper and many more countries could use it. This would be very useful in poor countries. The air in big cities would also become much cleaner and healthier as a result. Society and culture The Internet will help to create more worldwide friendships. Families may spend more time together as people will be able to do 24-hour online banking and shopping. Technology The new science of "nanotechnology" (very small robots or machines) will make all sorts of products smaller and lighter. Very, very small machines could take away rubbish, make things in factories, and help inside the human body by taking away fat. By 2012 people will be able to wear these small machines that look like watches, which will give them lots of information about their body and keep them healthy.
Question: What does the World Future Society do?
Options: (A) Look at how technology will make people happy. (B) Look at how technology will change the world. (C) Make technology work better for themselves. (D) Make small machines to make us healthier.
[EX A]:
B