The vitamins necessary for a healthy body are normally supplied by a good mixed diet, including a variety of fruits and green vegetables. It is only when people try to live on a very _ diet, say that when trying to lose weight, that it is necessary to make special provisions to supply the missing vitamins. An example of the dangers of a restricted diet may be seen in the disease known as "beri-beri", which used to make large numbers of Eastern people who lived mainly on rice suffer. In the early years of last century, a Dutch scientist named Eijkman was trying to discover the cause of beri-beri. At first he thought it was transmitted by a germ . He was working in a Japanese hospital, where the patients were fed on polished rice which had had the outer coverings removed from the grain, it was thought this would be easier for weak and sick people to digest. Eijkman thought his germ theory was proved when he noticed the chickens in the hospital yard, which were fed on remains from the patients' plates, were also showing signs of the disease. He then tried to separate the germ, which he thought was causing the disease, but his experiments were interrupted by a hospital official, who ordered that the rice without coverings, even though left over by the patients, was too good for chickens. It should be recooked for the patients, and the chickens should be fed on cheap, rough rice with the outer coverings still on the grain. Eijkman noticed that the chickens began to recover on the new diet. He began to consider the possibility that eating unmilled rice somehow prevented or cured beri-beri--even that a lack of some ingredient in the coverings may be the cause of the disease. Indeed this was the case. The element needed to prevent beri-beri was shortly afterwards separated from rice coverings and is now known as vitamin B. The milled rice, though more expensive, was in fact causing the disease the hospital was trying to cure. Nowadays, this terrible disease is much less common thanks to our knowledge of vitamins. The ingredient missing from milled rice _ A) was vitamin B B) did not affect the chickens C) did not result in beri-beri D) was named the Eijkman vitamin
A

Look closely at ,your hands-are they clean? It doesn't matter how many times you was your hands. They're still crowded with microbes, which are also called "germs" or "bacteria". Microbes are everywhere. But don't worry-most microbes don't harm you. and many actually help you stay alive. Now, scientists say the microbes that live on our hands could be used in a surprising way: fighting crime. When police visit the scene of a crime, they often look for fingerprints to try to identifythe criminal. But according to a recent study, investigators could even use microbes to help break a criminal case. Every person has his or her own set of microbes that live on their hands, according to scientists at,the University of:Colorado. That means the mix of different kinds of microbes on everybody's hand is unique-much like one's fingerprint. The scientists wanted to know whether this microbe mix could be used as a new kind of fingerprint-especially in a crime scene where fingerprints might be hard to find. And policemen use forensics such as studying fingerprints to identify the criminal. "Microbe fingerprints are harder to hide," said Noah Fierer, one of the scientists. "You can't sterilize(......) a surface just by wiping it off. " His team compared the bacteria on the hands of 273 people with the bacteria found on each person's computer keyboard. For the study, the keyboards had been used only by the people who were being tested. The study showed that the mix of microbes from each per- son's hands matched the mix of microbes on that person's keyboard. The scientists were easily able to tell the 273 people apart-just by looking at their keyboards. But there are a lot more than 273 criminals. Other scientists wonder whetherthe microbe fingerprint can really be that useful. Fierer agrees that scientists have a lot more work to do before the microbe fingerprint will be a useful tool. The main idea of the passage is about _ . A) the importance of fingerprints B) how to clean our hands C) the usefulness of microbes D) different germs on our hands
C

"Choo,Choo!"Here comes the Chunnel train. Get aboard if you want to learn more about this underground transportation system. This is an unusual form of transportation, because it is a tunnel that trains travel through and not an actual form of transportation. The Chunnel is actually the English nickname for the Channel Tunnel. In French,it is called le tunnel sous la Manche. It is a rail tunnel beneath the English Channel at the Straits of Dover. It connects Cheriton in Kent, England with Sangatte in northern France. It is the second longest rail tunnel in the world. Did you know that the British and the French had a race while they were building the Chunnel? The race was to see who could get to the middle of the tunnel first. The British won by a little bit. It took 15,000 workers over seven years to dig the tunnel. The tunnel was finished in 1994. The completed Chunnel cost about $21 billion. But it all paid off, because it became very popular, very quick. Millions of people use it. Now it is getting even more popular. There are three complete tunnels in the Chunnel. The two outside ones are the passenger trains. The small inner one is a guidance train. The guidance train is not used for transportation. Each track is exactly parallel to each other. There are four different train systems in the Chunnel. The Eurostar is a high speed passenger service that connects London, Paris, Brussels and Lille. The Eurotunnel shuttle is a rail ferry service. These shuttles carry cars and vans. These are railcars that allow drivers to drive their vehicles on and off. There are also two Eurotunnel goods service trains. Now you know more about the Chunnel. Everybody off,this is the last stop. The Eurotunnel shuttle is intended to carry _ . A) passengers B) drivers and their vehicles C) goods D) staff members of the Chunnel
B