Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
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Question: A house of cards? Sounds unbelievable, doesn't it? Not if the architect is 31-year-old Bryan Berg. He's made a career out of building fantastic card houses, stadiums, capitols, castles -- and the world's tallest card tower. How does he do it? Bryan's structures are amazing because they are made entirely of perfectly balanced, freestanding playing cards. He never uses glue, tape, or anything else to hold the cards together. Nor does he fold the cards. He's discovered another way to make a strong house of cards, using a trick from nature. To make plants strong, nature builds them with cells that have tough walls. Rows and rows of these cells form a grid that helps leaves and stems keep their shape. Bees use the same kind of repeating pattern to create strong honeycombs, where they live and store honey. Bryan designs similar grids, using cards to create a repeating pattern of cells. He begins with a single cell made by balancing four cards against one another to form a box. Then he repeats the cell over and over, expanding outward to form the grid, which makes a good foundation for a strong card structure. The larger the grid, the more weight it can carry. Sometimes Bryan uses several cards, instead of just one, to construct the cell walls, making the grid even stronger. The trick, he tells kids when he speaks in classrooms, is to place your cards as tightly together as possible when laying out your grid, making sure the cards are not leaning at all. After building this solid base, Bryan lays cards across the top to make the floor for the next "story" of the building. He may add towers, columns, steeples, or domes. Using the principle of repeating cells, Bryan builds structures of amazing strength. In the Cards Not surprisingly, Bryan has always been interested in building things. Growing up on a "big, old farm" in rural Iowa, he had plenty of room to play. "We were in the middle of nowhere," Bryan remembers, "with lots of space to do whatever we wanted. I was always making something, using things like sticks or bales of hay." Bryan's grandfather taught him how to stack cards. Bryan's two interests -- building and card stacking -- soon combined. But stacking in his family's farmhouse was challenging. "Our old house had wood floors that weren't all level," he reports. "And they weren't very firm. When people walked around, it was like 'earthquake action.' It was a challenge to build something that wouldn't fall down immediately." Bryan constructed tower after tower; he went through a lot of trial and error before he built anything taller than himself. When he placed a few decks of cards on top of his grid, he discovered how strong it was. Bryan's towers began to grow taller. How Tall Is Too Tall? Bryan's first Guinness World Record for the world's tallest card tower came in the spring of 1992, when he was in high school. Learning that the world record was 12 feet 10 inches, Bryan built a slim tower that topped out at 14 feet 6 inches. Done as a project for his geometry class, it took him 40 hours and 208 decks of cards. Since then he's gone on to win world records for even taller buildings. His latest winner measured 25 feet 3.5 inches and used about 2,400 decks of cards. _ Why don't these towers fall down? The key is in a good solid base, a repeating pattern of stories, and a tapering top. Bryan likes to point out how card buildings resemble real ones. They are built cell by cell, story by story. The separate parts make one strong whole. The heavier the building, the stronger and more stable it is. But the weight can't all be at the top. After spending so much time building something so cool, Bryan admits it's sometimes painful to see his structures destroyed. But he compares his work to the building of a sandcastle or an ice sculpture.

Answer: What was Bryan's first world record?


Question: Energy from the Sun comes from the lightest element, hydrogen, fusing together to create the second lightest element, helium. Nuclear fusion on the Sun releases tremendous amounts of solar energy. The energy travels to the Earth, mostly as visible light. The light carries the energy through the empty space between the Sun and the Earth as radiation. Solar energy has been used for power on a small scale for hundreds of years, and plants have used it for billions of years. Unlike energy from fossil fuels, which almost always come from a central power plant or refinery, solar power can be harnessed locally (Figure 1.1). A set of solar panels on a homes rooftop can be used to heat water for a swimming pool or can provide electricity to the house. Societys use of solar power on a larger scale is just starting to increase. Scientists and engineers have very active, ongoing research into new ways to harness energy from the Sun more efficiently. Because of the tremendous amount of incoming sunlight, solar power is being developed in the United States in southeastern California, Nevada, and Arizona. Solar panels supply power to the Interna- tional Space Station. Solar power plants turn sunlight into electricity using a large group of mirrors to focus sunlight on one place, called a receiver (Figure 1.2). A liquid, such as oil or water, flows through this receiver and is heated to a high temperature by the focused sunlight. The heated liquid transfers its heat to a nearby object that is at a lower temperature through a process called conduction. The energy conducted by the heated liquid is used to make electricity. This solar power plant uses mirrors to focus sunlight on the tower in the center. The sunlight heats a liquid inside the tower to a very high temperature, producing energy to make electricity. Solar energy has many benefits. It is extremely abundant, widespread, and will never run out. But there are problems with the widespread use of solar power. Sunlight must be present. Solar power is not useful in locations that are often cloudy or dark. However, storage technology is being developed. The technology needed for solar power is still expensive. An increase in interested customers will provide incentive for companies to research and develop new technologies and to figure out how to mass-produce existing technologies (Figure 1.3). Solar panels require a lot of space. Fortunately, solar panels can be placed on any rooftop to supply at least some of the power required for a home or business. This experimental car is one example of the many uses that engineers have found for solar energy. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL:

Answer: the source of solar power is nuclear


Question: I wish there would be a way to describe China in simple terms but that's impossible. For the most part Chinese people are friendly, easy-going and optimistic. They are curious and unusually patient and they are also the hardest-working people I have ever met. In China, family is everything. In my English classes when the students were asked what they would do if they only had a few hours to live, most students told me how they would spend their last few hours with their families and parents. Many times the subjects in the classes center on families and friends. I teach many students a year, talking to them freely. The cost of living here is very low compared with that of the US. The city of Xiang Fan I live in isn't large and I live better. Non-imported foods are very cheap, so are clothing and articles of everyday use. The cost of public transportation is very low, too. Chinese value education. However, it is reported that many children can't afford the expenses of schooling and are forced to leave school in some poor area in China. But they organized Project Hope many years age. It creates conditions for the poor children to go back to school. In my opinion, Project Hope is of great importance to the development of the rural education. When we read news of China in the west, rarely, if ever, will we see anything mentioned of the positive changes China has gone through. While it is true that economic miracles have not reached many areas of China, but we also have the same problems. When I am asked which country I consider better. China or the US, my answer has always been the same, "We are not worse or better than each other, we are only different."

Answer:
What are not cheap in China in the author's opinion?