单选题 Famed singerSteve Wonder can't see his fans dancing at his concerts. He can't see the hands of his audience as they applaud wildly at the end of his Superstition. Blind from birth, Wonder has waited his whole life for a chance to see. Recently, Wonder visited Mark Humayan, a vision specialist. He thought that a new device currently being studied by Humayan might offer him that chance. The device, a retinal prosthesis, is a tiny computer chip implanted inside a patient's eye. The chip sends images to the brain and allows some sightless people to see shapes and colors. Wonder hoped the retinal prosthesis might work for him. "I've always said that if ever there's possibility of my seeing," said Wonder, "then I would take the challenge." Unfortunately for Wonder, that challenge will have to wait. Humayan explained that the device isn't ready for people who have been blind since birth. Their brains may not be able to handle signals from a retinal prosthesis because their brains have never handled signals from a healthy eye. However the retinal prosthesis and other devices show great promise in helping many other sightless people who once had vision see again. Perhaps one day soon, some formerly sightless people may be in Wonder's audience looking up—and seeing him—for the very first time. Wonder's willingness to take part in retinal prosthesis studies and the results of those studies are giving new hope to people who thought they would be blind for the rest of their lives. More than one million people in the United States are considered legally blind, meaning that their eye- sight is severely impaired. Another one million are totally blind. Two types of specialized cells in the retina—rods and cones—are critical for proper vision. Light enters the eye and falls on the rods and cones in the retina. Those cells convert the light to electrical signals, which travel through the optic nerve to the brain. The brain interprets those signals as visual images. Rods detect light at low levels of illumination. For instance, rods allow you to see faint shadows in dim moonlight. Cones, on the other hand, are most sensitive to color.Some diseases can damage cells in the retina. For instance, macular degeneration causes blind ness and other vision problems in 700,000 people in the United States each year. The condition i caused by a lack of adequate blood supply to the central part of the retina. Without blood, the rods, cones, and other cells in the retina die. Devices such as the retinal prosthesis won't prevent or cure our eye diseases, but they ma help patients who have eye disorders regain some of their vision. Different forms of retinal presto sis are currently being developed. On one type, a tiny computer chip is embedded in the eye The chip has a grid of about 2,500 light-sensing elements called pixels. Light entering the eye strikes the pixels, which convert the light into electrical signals. The pixels then send the electrical signals to nerve cells, behind the retina. Those cells send signals vi the optic nerve to the brain for interpretation. Many people who have had a retinal prosthesis implanted say they can see shapes, colors and movements that they couldn't see before. "It was great," said Harold Churchey, who n ceived his retinal prosthesis 15 years after he became totally blind. "To see light after so long—was just wonderful. It was just like switching a light on."

单选题The ozone layer plays as great a role in the stability of spaceship Earth as ______ the waters of its lakes, ponds, oceans, rivers, and streams.

单选题Further education is officially (described as) the post-secondary stage of education, (comprised) all vocational and convocational (provision made) for young people who have left school, (or for adults).

单选题There is a sale at Hamfridge's next week with ______ in all departments. A. decreases B. subtractions C. reductions D. accounts

单选题The article was written in order to ______.

单选题Nearly all trees have seeds that fall to the earth, take root, and eventuall______

单选题Changing from solid to liquid, water takes in heat from all substances near it, and this ______ produces artificial cold surrounding it.

单选题The poison produced by the spider's skin is so ______ that it will paralyze a bird or a monkey immediately. A.lethal B.liable C.tedious D.profound

单选题Looming over the debate about human interference in the world's boreal forests is an as yet unanswerable question: Will the effects of global warming eventually {{U}}dwarf{{/U}} man's impact?

单选题The bombing campaign is______years of civil conflict and drought to create an environmental crisis.

单选题The (five-year) project would (expose) (educational) disadvantaged students to (experiences) both creative and enriching.

单选题The policeman wrote down all the particulars of the accident.

单选题{{B}}Passage 1{{/B}} Distance education is enrollment and study with an educational institution that provides lesson materials prepared in a sequential and logical order for study by students on their own. When each lesson is completed, the student mails or transmits the assigned work to the institution for correction, grading, comment, and subject matter guidance by qualified instructors. Corrected assignments are returned promptly to the student. This exchange provides a personalized student-teacher relationship. If a student slows his or her pace or fails to send assignments, the school provides encouragement. Although some institutions provide employment placement information and assistance, no reputable school ever guarantees a job to graduates. Distance education and self-study are different. Self-study materials provide no instructional service. Corrected assignments, examinations, and special help provided by a qualified facility are vital to a good learning situation. However, these are not part of self-study. There are many self-study courses and recordings available, and they may have value, but they clearly are not correspondence or distance education courses. Some institutions offer combination courses that provide training-in-residence for students who complete their distance education lessons. In-service or on-the-job training is required or provided with other courses and is a feature of many vocational distance education programs. Quality distance education institutions screen prospective students to assure that only those who can benefit from the courses are enrolled. While there are educational prerequisites for some academic subjects, interest and aptitude are the primary factors leading to success in most distance education courses. Because they provide alternative educational opportunities, distance education institutions try not to deny a prospective student the opportunity to succeed in a course; interest and experience are good indicators of future Success. Distance education courses vary greatly in scope, level, and length. Some have few lessons and require only weeks to complete, while others have a hundred or more assignments requiring three or four years of conscientious study. Also, a wide variety of subjects is offered. Subjects include yacht design, accounting, medical transcription, nutrition, robotics, travel agent training, gun repair, gem identification, computer programming, catering and cooking, and earning an entire high school diploma, just to name a few. There is an increasing recognition of "distance education" and many colleges offer credit for their distance learning courses or accept some distance education credits of resident students working toward a degree. In fact, many distance education institutions award their own academic degrees. Acceptance of students and awarding of academic credit is the prerogative of the receiving academic institution. Also, the employing organization may set its own credit acceptance policies.

单选题The laser represents a true marriage between science and technology, the men who devised it were______engineers and physicists. A. spontaneously B. simultaneously C. instantaneously D. homogeneously

单选题It is regrettable that the author saved many of his most brilliant lines for the By that time, most of the audience had left.

单选题The major obstacle to the reform in New Orleans, ______, is money.

单选题It does not alter the fact that he was the man______ for the death of the little girl.

单选题The river was______with industrial waste from the nearby factory.