In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.

[EX Q]: Article: What if we could replace oil with a fuel which produced no pollution and which everybody had equal access to? The good news is that we can. In fact, we are swimming in it--- literally. Hydrogen is one of the building blocks of the universe. Our own sun is basically a big, dense cloud of the stuff. And hydrogen can be used to create electricity for power, heat and light. The problem is that hydrogen is everywhere and nowhere at the same time. It does not exist as a material on its own, but is always part of something else. So it has to be separated before it can be used. Most commercial hydrogen in use now is created from natural gas. As oil will start to run out in around the year 2030, it makes sense to produce as much hydrogen as possible as soon as we can. But natural gas supplies will also begin to run out soon after. Another source is needed. Researchers are now using electricity to make water into hydrogen. Companies are working on the problem in their own areas. The first commercial hydrogen "fuel cells" for computers and mobile phones have already come on to the market. Auto companies have also invested over US $2 billion in the production of hydrogen fuelled cars. The nations of a hydrogen fuelled planet would not fight over energy recourses. There would be a great reduction in pollution. The only by-product of creating hydrogen is pure drinking water--- something that is very scarce in many parts of the world. But that is not where the good news ends. Once the costs of producing hydrogen have been brought down, it will possibly provide power for a third of the Earth's population that has no electricity. And electricity creates wealth. In South Africa over the last decade there has been a large programme of electrification. Thanks to the programme, people do not have to spend their days looking firewood to burn for heat. And with electric light, they can work long into the night. Some scientists see radical changes in the way the human race co-operates. Hydrogen creates electricity, and is also created by _ . With dual use fuel cells, everyone who consumes energy could also produce it. Late at night, a man drives home in London and connects his car into the "world-wide hydrogen web," which it supplies with electricity. A few hours later, a man in Beijing uses that electricity to power the hydrogen cell in his car. Hydrogen could be the first democratic energy source. Like all dreams of the future, it seems very far away. But the threat of war and terrorism in the Middle East has made governments and businesses more aware of the need to end oil dependency and spend more time and money on hydrogen resource. So maybe the threat of war is not a completely bad thing for the future of the human race.
Answer: It has to be separated from other materials.
[EX A]: What is the problem with using hydrogen as energy?

[EX Q]: Article: Nearly 60 million visitors flooded to the 384 national parks across America every year. And you won't have to wander far from home to enjoy one of these national treasures, with Michigan's Isle Royale National Park nearby. Located 56 miles from Copper Harbor on Michigan's Upper Peninsula, the park remains _ that can only be reached by tour boat. With the exception of the Rock Harbor Lodge, which offers both rooms with private baths and accommodations in the form of small cottages, the 572,000 acres that make up the 45-mile-long park are rough, threaded with hiking paths that lead to tents-only campsites. You are likely to see a deer crossing mist-covered ponds in search of breakfast, gaze bald eagles flying overhead, or hear a beaver clapping its tail on the water. If you are especially lucky, you might even glimpse a grey wolf, nearly dying out from hunting on the mainland. Plenty of hiking paths open the area to exploration. The 4-mile Stroll Path winds through various trees and offers a tour of the island's history, including prehistoric Indian mines. The Jungle Path leads to Scoville Point----a perfect picnic spot surrounded on three sides by the shining waters of Lake Superior. You can also rent a boat at the park's service center and row down the shore to the Rock Harbor Lighthouse. Here park's service employees use nets to show how lake fishes used to be caught by the original local people. Their catch ends up on the dinner menu at the Rock Harbor Lodge. The park is open from mid-April through October; Rock Harbor Lodge is open from Memorial Day weekend until just after Labor Day.
Answer: Food provided by Rock Harbor Lodge is shipped from outside.
[EX A]: What can we infer from the passage?

[EX Q]: Article: Old age may not sound exciting.But recent findings offer good news for older pepole and for people worried about getting older. Researches found that people become happier and experience less worry after they reach the age of fifty.In fact,they say by the age of eighty--five,people are happier with their life than they were when they were eighteen years old. The findings came from a survey of more than 340,000 adults in the United States.The Gallup Organization questioned them by telephone in 2008.At that time,the people were between the ages of eighteen and eighty--five.The searches asked questions about emotions like happiness,sadness and worry.They also asked about mental or emotional stress. Arthur Stone in the Department of Psychiatry and Behavioral Science at Stony Brook University in New York led the study.His team found that levels of stress were highest among adults between the ages of twenty--two and twenty--five.The findings showed that stress levels dropped sharply after people reached their fifties.Happiness was highest among the youngest adults and those in their early seventies.The people least likely to report feeling negative emotions were those in their seventies and eighties. The study also showed that men and women had similar emotional patterns as they grew older.Hower,women at all ages reported more sadness,stress and worry than men.Researchers say they do not know why happiness increases as people get older.One theory is that,as people grow older,they grow more thankful for what they have and have better control of their emotion .They also spend less time thinking about bad experiences. The researchers also considered possible influences like having young children,being unemployed or being single.But they found that influences like these did not affect the levels of happiness and well--being related to age.
Answer: They telephoned people between the ages of 18 and 85.
[EX A]:
How did the researchers find older people happier?