单选题It is said the houses along this street will soon be pulled down .

单选题Eta Carinae is hard to observe because

单选题It is unnecessary for a neighborhood baker to use a computer in his shop.

单选题The author's cousin Harry quite clearly had a rather Uweird/U sense of humour.

单选题The report advocated setting up day training colleges. A．supposed B．excited C．suggested D．discussed

单选题A．red flag was placed there as a token of danger. A．sign B．substitute C．proof D．target

单选题We will meet in the office at approximately 3:30 in the afternoon.A. aboutB. almostC. probablyD. rarely

单选题It is easy to misjudge the strength of the wind.

单选题Certain colors when incorporated into the decor of a room can produce a {{U}}cozy{{/U}} atmosphere.

单选题Today many countries are

单选题Smart Windows Windows not only let light in to cut down on electricity use for lighting, but the light coming through the window also provides heat. However, windows are not something people typically associate with an advanced technology. Researchers are now working on new technologies that enable a window to quickly change from clear to dark and anywhere in between easily. "It took us a long time to figure out what a window really is," says Claes Granqvist. He"s a professor of solid-state physics at Uppsala University in Sweden. "It"s contact with the outside world. You have to have visual contact with the surrounding world to feel well." So, windows and natural light are important for improving the way people feel when they"re stuck indoors. Yet, windows are the weak link in a building when it comes to energy and temperature control. In winter, cold air leaks in. When it"s hot and sunny, sunlight streams in. All of this sunlight carries lots of heat and energy. And all of this extra heat forces people to turn on their air conditioners. Producing blasts of cold air, which can feel so refreshing (使人清新的), actually sucks up enormous amounts of electricity in buildings around the world. Windows have been a major focus of energy research for a tong time. Over the years, scientists have come up with a variety of strategies for coating, glazing (用玻璃覆盖), and layering windows to make them more energy efficient. Smart windows go a step further. They use chromogenic (发色的) technologies which involve changes of color. Electrochromic (电致色的) windows use electricity to change color. For example, a sheet of glass coated with thin layers of chemical compound such as tungsten oxide (氧化钨) works a bit like a battery. Tungsten oxide is clear when an electric charge is applied and dark when the charge is removed, that is, when the amount of voltage (电压) is decreased, the window darkens until it"s completely dark after all electricity is taken away. So applying a voltage determines whether the window looks clear or dark. One important feature that makes a smart window so smart is that it has a sort of "memory". All it takes is a small change of voltage to turn the window from one state to the other. Then, it stays that way. Transitions take anywhere from 10 seconds to a few minutes, depending on the size of the window. The development of smart windows could mean that massive air conditioning systems may no longer be needed. "In the future," Granqvist says, "our buildings may look different."

单选题U.S. Scientists Confirm Water on Mars NASA scientists said that Mars was covered once by vast lakes, flowing rivers and a variety of other wet environments that had the potential to support life. Laboratory tests aboard NASA's Phoenix Mars Lander have identified water in a soil sample; the lander's robotic arm delivered the sample Wednesday to an instrument that identifies vapors produced by the heating of samples. "We have water," said William Boynton of the University of Arizona, lead scientist for the Thermal and Evolved-Gas Analyzer, or TEGA "This is the first time Martian water has been touched and tasted. " The robotic arm is a critical part of the Phoenix Mars mission. It is needed to trench into the icy layers of northern polar Mars and deliver samples to instruments that will analyze what Mars is made of, what its water is like, and whether it is or has ever been a possible habitat for life. The soil sample came from a trench approximately 2 inches deep. When the robotic arm first reached that depth, it hit a hard layer of frozen soil. Two attempts to deliver samples of icy soil on days when fresh material was exposed were foiled when the samples became stuck inside the scoop. Most of the material in Wednesday's sample had been exposed to the air for two days, letting some of the water in the sample vaporize away and making the soil easier to handle. "Mars is giving us some surprises," said Phoenix principal investigator Peter Smith of the University of Arizona. "We're excited because surprises are where discoveries come from. One surprise is how the soil is behaving. The ice-rich layers stick to the scoop when poised in the sun above the deck, different from what we expected, from all the Mars simulation testing we've done so far." Since landing on May 25, Phoenix has been studying soil with a chemistry lab, TEGA, a microscope, a conductivity probe and cameras. The science team is trying to determine whether the water ice ever thaws enough to be available for biology and if carbon-containing chemicals and other raw materials for life are present. The mission is examining the sky as well as the ground. A Canadian instrument is using a laser beam to study dust and clouds overhead. "It's a 30-watt light bulb giving us a laser show on Mars," said Victoria Hipkin of the Canadian Space Agency. A full-circle, color panorama of Phoenix's surroundings also has been completed by the spacecraft. "The details and patterns we see in the ground show an ice-dominated terrain as far as the eye can see," said Mark Lemmon of Texas A & M University, lead scientist for Phoenix's Surface Stereo Imager camera. "They help us plan measurements we're making within reach of the robotic arm and interpret those measurements on a wider scale. /

单选题In order to{{U}} survive{{/U}} man needs to consume food and water．

单选题Youth hotels provide inexpensive lodging for young people throughout the United States and in other countries.

单选题These programmes are of immense value to old people A. natural B. fatal C. tiny D. enormous

单选题Archaeologists (考古学家) have discovered remains of million-year-old animals in excavations.

单选题The waitress {{U}}showed{{/U}} me to the table we have booked this afternoon.

单选题After the collision, he examined the considerable wreck to his car.A. ruinB. destructionC. damageD. injury

单选题The river was {{U}}contaminated{{/U}} with waste.

单选题He was said to have been {{U}}removed{{/U}} from the position of manager for a recent confii~ with an important customer.