Back in old times, people had little knowledge about the universe and nature. Things we now consider to be common sense were mysteries to our ancestors. Over the years, major breakthroughs have been made in science and many phenomena have been explained. But still, there are always questions we can't yet answer, and The Guardian has listed some of them. 1. What makes us human? Just looking at your DNA won't tell you - human DNA is 99 percent _ to that of the chimpanzee and, believe it or not, 50 percent identical to a banana's! A lot of the things we once thought were unique about us - language and tool use, recognizing ourselves in the mirror and so on - have since been seen in other animals. Perhaps it's our culture that makes the difference or maybe our ability to use fire. It's also possible that our capacity   for co-operation and our trading skills are what make us unique. 2. Why do we dream? Given the fact that we spend around a third of our lives sleeping, shouldn't we know everything about it? Unfortunately, scientists are still searching for a complete explanation of what happens when we sleep and why we dream. Austrian psychologist Sigmund Freud believed dreams were the expressions of wishes that we can't fulfill in our real lives. Others have wondered whether dreams are just random "noise" coming from a sleeping brain. 3. Could we someday live forever? Apart from accidents, most people die because of diseases that can be treated and aging. And since many diseases, such as diabetes  and cancer, are diseases of aging, treating aging itself could be the key to extending our lives. Our knowledge of what causes us to age - and what allows some animals to live longer than others - is expanding rapidly. And though we haven't quite worked out all the details, we've worked out some pieces of the puzzles such as DNA damage and metabolism  , which are all leading to the invention of drugs that can slow down the aging process. If we're lucky enough to lengthen our lives, we might even get to see the day when... The main point of the passage is   _  . A) to inform people of the knowledge about the universe and nature B) to introduce major breakthroughs that have been made in science C) to present some questions we can't yet answer D) to explain what were once mysteries to our ancestors
C

Mr. Jackson was tired of living in his old house in the countryside and wanted to sell it and buy a better one. He tried to sell it for a long time, but was not successful, so at last he decided to go to an estate agent. The agent advertised  the house straight away, and a few days later, the owner saw a very beautiful photograph of his house, with a wonderful description of his garden in an expensive magazine. Having read the advertisement through, the house owner hurried to phone the estate agent, saying, "I'm sorry, Mr. Jones, but I've decided not to sell my house after all." "Why?" the agent asked in a surprised voice. "Because from the advertisement in that magazine I can see it's just the kind of house I've wanted to live in all my life." Mr. Jackson wanted to sell his house because   _  . A) he needed some money to support his family B) his house was too old to live in C) he wanted some money to buy a new one D) he didn't want to live in the house any longer
D

Runners in a relay race pass a stick in one direction. However, merchants passed silk, gold, fruit, and glass along the Silk Road in more than one direction. They earned their living by traveling the famous Silk Road. The Silk Road was not a simple trading network. It passed through thousands of cities and towns. It started from eastern China, across Central Asia and the Middle East, and ended in the Mediterranean Sea. It was used from about 200 BC to about 1300 AD, when sea travel offered new routes. It was sometimes called the world's longest highway. However, the Silk Road was made up of many routes, not one smooth path. They passed through what are now 18 countries. The routes crossed mountains and deserts and had many dangers of hot sun, deep snow and even battles. Only experienced traders could return safe. The Silk Road got its name from its most prized product. Silk could be used like money to pay taxes or buy goods. But the traders carried more than just silk. Gold, silver, and glass from Europe were much found in the Middle East and Asia. Horses traded from other areas changed farming practices in China. Indian merchants traded salt and other valuable goods. Chinese merchants traded paper, which produced an immediate effect on the West. Apples traveled from central Asia to Rome. The Chinese had learned to graft   different trees together to make new kinds of fruit. They passed this science on to others, including the Romans. The Romans used grafting to grow the apple. Trading along the Silk Road led to world-wide business 2,000 years before the World Wide Web. The people along the Silk Road did not share just goods. They also shared their beliefs. The Silk Road provided pathways for learning, diplomacy, and religion. What is the best title for the passage? A) The Silk Road: Past and Present B) The Silk Road: East Meets West C) The Silk Road: Routes Full of Dangers D) The Silk Road: Pathways for Learning
B

People used to think that wetlands were wasted land. Developers would drain them with ditches ,fill them in with tons of soil,and build houses,schools,and parking areas on them.Then scientists began to realize the important role wetlands played in the environment. Wetlands act like giant sponges  during storms.They soak up extra storm water and afterward release it slowly back into the water cycle.This helps prevent flooding. Towns where people have drained wetlands have found that in a big storm,their streets and homes are often flooded because there are no wetlands to soak up the excess water. Wetlands also act as giant filters where pollutants are absorbed and dissolved over time.Though wetlands can become polluted from dumping,wastewater,and fertilizer runoff from farm fields,they are able to process some pollutants over time because of all the microorganisms and plants living there. Wetlands are especially important for providing homes and breeding grounds to millions of birds,fish,and amphibians worldwide. Many wetlands have become national wildlife refuges ,where you can go to take pictures and look at birds and animals. The Everglades are a huge wetland that once covered more than four million acres of southern Florida. Sometimes called the "river of grass",the Everglades are a shallow sheet of water that slowly flowed across a grassy plain. In the late 1800s people began draining parts of the Everglades for development. Roads were built and towns sprang up.The Everglades shrank to half its original size. Cities like Miami grew up where once there was a thriving wetland. Sewage and waste from the cities were pumped into the remaining wetlands. Over time scientists began to see the importance of the Everglades. Even with its smaller size,the Everglades filtered the pollutants coming from the cities,absorbing the worst of it like a sewage treatment plant. During storms the Everglades protected the cities from storm surge flooding. They also are just a great place to visit and see wildlife. Why can wetlands be compared to giant sponges? A) They absorb extra water from storms. B) They become large or small in size. C) They absorb pollutants and dissolve them. D) They are made of soft soil.

A