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Read the passage carefully, then choose the correct answer.
Coal, oil, and natural gas supply modern civilization with most of its power. However, not only are supplies of these fuels limited, but they are a major source of pollution. Therefore, it's important to improve, explore and develop such alternative energy sources as nuclear, water, solar and wind power. Each of these alternatives, however, has advantages and disadvantages.
Nuclear power plants efficiently produce large amounts of electricity without polluting the atmosphere; however, they are costly to build and maintain, and they create the difficult problem of what to do with nuclear waste. Hydroelectric power is inexpensive and environmentally safe, but impractical for communities located far from moving water. Wind power is a pollution-free source of renewable energy but it cannot be used in many parts of the world where there is insufficient wind. Solar power is renewable, it does not cause pollution and it does not add the earth's heat load. However, it is difficult to collect and store. Solar power also requires expensive equipment. 
Wind power___________.
A.cannot be used in places that has strong wind 
B.is never completely used up 
C.is a source of pollution
D.cannot replace itself
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Read the passage carefully, then choose the best answer for each question.
HAVE ALIENS VISITED US?
Many people have stories about seeing aliens. Here are two.
Judy Varns works for a group called the Mutual UFO Network. The purpose of this group is to research UFO sightings. Varns thinks a place called Area 51, in Nevada in the U.S., may be the best place on Earth to see UFOs. One day, she took some photos in the area and saw something she thinks is a UFO. "We saw this little disk-shaped thing in our photos. It's kind of exciting," she says.
Pat Travis lives near Area 51. One night, she saw a strange light in the sky. The light's movements were very unusual. Travis saw the lights move sideways and up and down. She saw them make many strange moves. Travis thinks it was a UFO.
Secrets of Area 51
Some people think Area 51 is where the U.S. Air Force keeps secrets, like UFOs that came to Earth and the aliens inside them. But really, Area 51 is a place the U.S. Air Force uses to test new technology, such as new kinds of aircraft.
James McGaha is a pilot who flew airplanes at Area 51. "There is absolutely no UFO activity at Area 51," he says. "No flying saucers, no live aliens, no dead aliens."
So what did Varns and Travis see? Bill Fox worked at Area 51, too. He thinks he knows the answer. "We did build some strange-looking airplanes," he says. "I could see why some people would think they were UFOs."
So are UFOs real? You'll have to decide for yourself. But if you do visit Nevada, keep your eyes on the skies!
What does “I could see why some people would think they were UFOs” mean?
A.I agree with people who believe in UFOs.
B.I saw UFOs near Area 51 with my own eyes.
C.I understand why some people think they saw UFOs.
D.I claim that UFOs are real because many people have seen them.

Read the passage carefully, then choose the best answer for each question.
THE HISTORY OF PIZZA
Today, pizza is one of the world's favorite foods. All over the world, people make different pizzas, with different ingredients. But where does pizza come from? And who made the first one?
The First Pizza
People have been making pizza for a very long time. In the Stone Age, some people mixed flour with water to make dough. Then they cooked it on hot rocks. Over time, people started using the cooked dough as a plate, covering it with various other foods, herbs, and spices. They had made the world's first pizza.
A New Ingredient
Then—in the early 1500s—European explorers brought the first tomatoes back from the Americas. Tomatoes are a basic ingredient in many pizzas today. At first, however, most Europeans thought eating tomatoes would make them sick. So, for about 200 years, few people ate them.
Slowly, people learned that tomatoes were safe to eat, as well as tasty. In the early 19th century, cooks in Naples, Italy, started the tradition of putting tomatoes on baking dough. The flat bread soon became a favorite food for poor people all over Naples. In 1830, a cook in Naples took another big step in the history of pizza—he opened the world's first pizza restaurant.
A World Food
Today, about five billion pizzas are made every year around the world. In the U.S. alone, people eat about 350 slices every second! People may not know it, but every piece is a slice of history.
What does people started using the cooked dough as a plate mean?
A.People put other foods on top of the dough.
B.People cooked the pizza dough on hot rocks.
C.People used the same pizza dough again and again.
D.People cooked the pizza dough on a plate.

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