If you look at the night sky, you'll often see stars moving very quickly. In fact, they move much more quickly than they should according to their size and the laws of physics. Scientists do not completely understand why the speed of these stars is so high. But many believe the reason is that much of the universe is made of something called "dark matter". Groups of stars called galaxies, such as the Milky Way, might even be made up of 90 percent dark matter. How much something weighs depends on where it is. The same object weighs only half as much on Mars as it does on Earth and almost three times as much on Jupiter. So scientists prefer to talk about the mass of something rather than how much it weighs, because mass does not change. They can work out the mass of galaxies by measuring the distance between them and the speed they move at. Recently, Jorge Penarrubia, a senior academic at Edinburgh University, UK, and his team discovered something interesting: The mass of the Milky Way is only half as much as the mass of another nearby galaxy, Andromeda. This seems strange, and dark matter may explain why. Finding out more about dark matter could help us understand how the universe began, but this is not easy. Lots of scientists with different types of expert knowledge are working on the problem. We can't see dark matter, it's very difficult to measure and we can't find out its mass. Unlike stars, dark matter doesn't produce or reflect light. But we can make a good guess that it is there because of the way things move and the way light bends. Experts now think dark matter may be very different from the matter that we find on Earth. There may also be five times as much dark matter in the universe as ordinary matter. The author mentions the masses of the Milky Way and Andromeda mainly to _ . A) explain why the same object has a different weight on different stars B) compare the distance between the Milky Way and Andromeda C) show that studying dark matter could help to answer some scientific questions D) support the idea that scientists prefer to talk about mass instead of weight
C
(Question)
Yellowstone and Grand Tetons Multisport Tour In four great days, we discover waterfalls, wild animals, and natural hot springs in Yellowstone. In the Tetons, we rock climb, go biking in wildness and go boating on the Snake River's fun-filled rapids. DAY 1: Bridger-Teton--Upper Geyser Basin Ride a bicycle through the Bridger-Teton National Forest. Then head to Yellowstone and walk through Upper Geyser Basin and the world's largest active geysers . Witness Old Faithful's performance and settle into the comforts of classic Old Faithful Inn, dating from 1903. DAY 2: Jenny Lake-Grand Tetons Choose your own adventure! Spend the day in Grand Teton National Park hiking to Inspiration Point and Cascade Canyon. Or choose to hike along the shoreline of Jenny Lake for the whole day. DAY3: Hidden Falls--Grand Tetons Rock climb near Hidden Falls. Just bring a spirit of adventure, then leave the rest to our experienced guides. Or you can choose instead to take another hike, horseback ride or enjoy fishing in the area. DAY 4: Antelope Flats--Snake River--Jackson Ride a bicycle through wildlife-filled Antelope Flats before going boating for an exciting afternoon on the Snake River and the end of our journey in Jackson. Trip Details 4 Days/3 Nights Trip Type: Multisport Price: $1,798 (camping); $2,298 (inn & camping) Meeting Place: Jackson, Wyoming Dates: June 24-June 29 (Singles, Camping); July 08-July 13 (Family, Camping); July 29-Aug. 03 (Family, Inn & Camping) During the tour, on which activity will you spend the most time? A) Biking. B) Rock climbing. C) Rafting. D) Hiking.
(Answer)
D
Ques: The card using a built-in voice-recognition chip requires users to give a spoken password that it recognizes. The idea is to prevent thieves from using a stolen card to buy goods online. A model built by engineers in California packs a microphone, a loudspeaker, a battery and a voice-recognition chip into a standard-sized credit card. The card is the length and width of an ordinary credit card but about three times as thick. The company now plans to make it thinner. The voice card is based on an earlier Beep card technology designed to prevent fraud in online deals. The Beep card has no microphone, but has a built-in loudspeaker to utter an audible ID signal by a computer's microphone to an online server . By confirming that signal matches the information in the card, the server can make sure that the user is not simply keying in a credit card number but actually has the card in his hand. The ID code, which only the server knows, changes each time the card is used. This prevents fraudsters recording the beeps, noting the card details and then playing back the audible ID when they key in the details later. But this earlier Beep card technology cannot prevent illegal use of stolen cards. The new voice card can. The new voice card doesn't identify itself by its ID until it has confirmed the real user's spoken password. Thieves will be unable to use the card because even if they knew the password they would have to be able to copy the owner's voice with a high degree of accuracy. The challenge for Beep card has been to develop voice-recognition and audio circuitry . The voice-recognition credit is powered by a mini battery. To extend batter life, the electronics have only to be switched on when the card is being used. Pressing a button on the card's surface allows one to hear a female voice saying, "Say your password." If the voice-recognition software proves that the password is real, it sends its ID, which the server then identifies, allowing the deal to continue. What is the problem with the model card? A) It is too large. B) It is too thick. C) It can't be used online. D) It has no loudspeaker.
Ans: B
Ques:Students who say they never or hardly ever used dictionaries often speak English well but usually write poorly, because they make many mistakes. The students who use dictionaries most do not learn especially well either. The ones who look up every word do not read fast. Therefore they do not have time to read much .Those who use small two-language dictionaries have the worst problems. Their dictionaries often give one or two words as a translation of English. But one English word has many English translations in Chinese. The most successful students are those who use large college edition dictionaries with about 100,000 words but do not use them often, When they are reading these students first try to get the general idea and understand the new words from the context .Then they read and use the dictionary to look up only key words that they still do not understand. They use dictionaries more for writing. Also if they think a noun might have an unusual plural form or a verb might have an unusual past form, they check these in a dictionary. The writer tends to think that_. A) Choose a good dictionary, and you will succeed in learning English B) Dictionaries are not necessary to the students who learn English C) it is very important for the students to use good dictionaries properly . D) using dictionaries very often can't help to improve writing

Ans:
C