单选题Mycorrhizal fungi infect more plants than do any other fungi and are necessary for many plants to thrive, but they have escaped widespread investigation until recently for two reasons. First, the symbiotic association is so well-balanced that the roots of host plants show no damage even when densely infected. Second, the fungi cannot as yet be cultivated in the absence of a living root. Despite these difficulties, there has been important new work that suggests that this symbiotic association can be harnessed to achieve more economical use of costly super phosphate fertilizer and to permit better exploitation of cheaper. less soluble rock phosphate, Mycorrhizal benefits are not limited to improved phosphate uptake in host plants. In legumes, mycorrhzal inoculation has increased nitrogen fixation beyond levels achieved by adding phosphate fertilizer alone. Certain symbiotic associations also increase the host plant's resistance to harmful root fungi. Whether this resistance results from exclusion of harmful fungi through competition for sites, from metabolic change involving antibiotic production, or from increased vigor is undetermined.

单选题The orders will come into ______ on the l5th.

单选题We (are obliged) to grow up in skepticism, requiring proofs for every assertion about nature, (but) there is no way out (except) to move ahead and plug away, hoping for comprehension in the future (but) living in a condition of intellectual instability for long time.

单选题Mr. Murray remains a Udevout/U supporter of the new theory.

单选题He is a(n) ______ and well-behaved child, but his parents worry about him for he talks too little. A. obedient B. transient C. conscious D. passionate

单选题This week marks the 10th anniversary of the Alar apple scare, in which many American consumers were driven into a panic following the release of a report by an environmental organization claiming that apples containing the chemical Alar posed a serious health threat to preschoolers. The report was disseminated through a PR (Problem Report) campaign and bypassed any legitimate form of scientific peer review. Introduced to the American public by CBS' "60 Minutes," the unsubstantiated claims in the report led some school districts to remove apples from their school lunch programs and unduly frightened conscientious parents trying to develop good eating habits for their children. Last month, Consumers Union released a report warning consumers of the perils of consuming many fruits and vegetables that frequently contained "unsafe" levels of pesticide residues. This was especially true for children, they claimed. Like its predecessor 10 years earlier, the Consumers Union report received no legitimate scientific peer review and the public's first exposure to it was through news coverage. Not only does such reporting potentially drive children from consuming healthful fruits and vegetables, the conclusions were based on a misleading interpretation of what constitutes a "safe" level of exposure. Briefly, the authors used values known as the "chronic reference doses," set by the U. S. Environmental Protection Agency, as their barometers of safety. Used appropriately, these levels represent the maximum amount of pesticide that could be consumed daily for life without concern. For a 70-year lifetime, for example, consumers would have to ingest this average amount of pesticide every day for more than 25, 000 days. It is clear, as the report points out, that there are days on which kids may be exposed to more; it is also clear that there are many more days when exposure is zero. Had the authors more appropriately calculated the cumulative exposures for which the safety standards are meant to apply, there would have been no risks and no warnings. Parents should feel proud, rather than guilty, of providing fruits and vegetables for their children. It is well established that a diet rich in such foods decreases the risk of heart disease and cancer. Such benefits dramatically overwhelm the theoretical risks of tiny amounts of pesticides in food. So keep serving up the peaches, apples, spinach, squashes, grapes and pears.

单选题Cut off by the storm, they were forced to ______ food for several days.

单选题When college students ______ future employment, they often think of status, income and prestige.

单选题My calculation was wrong because 1 ______ one tiny point.

单选题The coalition parties have asked the government to consider using more funds to help support the {{U}}ailing{{/U}} market.

单选题{{B}}Passage 2{{/B}} Yeats was beginning to use a vocabulary freshly minted from the treasury of Gaelic literature, and many of the shorter poems in The Countess Kathleen and Various Legends and Lyrics (1892) deal with a mythology Ireland had well nigh forgotten and England never known. For Arthur and his Round Table Yeats substituted the very different Conchubar and his Red Branch Warriors, and Finn and his Fenians. The Red Branch cycle of legends included Fergus, whom Ness had tricked out of his kingdom so that her son Conchubar could rule over Ulster in his stead, and in Fergus and the Druid Yeats makes him avid for dreaming wisdom. Fergus was the unwitting agent of the doom of the Sons of Usna, Naoise the lover of Deirdre and his brothers Ardan and Ainle, who had accompanied the lovers to Scotland when they fled from Conchubar's wrath, for Deirdre was Conchubar's intended bride. Fergus had persuaded them to return against the wishes of Deirdre and had been tricked out of acting as their safe conduct. He joined with Maeve, Queen of Connaught, after this, in her raid on Ulster, in which Cuehulain achieved his great fame as Ulster's champion. Cuehulain is the Achilles of the Irish Saga, and he appears throughout Yeats's plays and poems, as warrior, as husband of Emer, as lover of Eithne Inguba, and of Aoife, as the unknowing killer of his own son and finally as victim of the sea.

单选题Mass transportation revised the social and economic,{{U}} fabric{{/U}} of the American city in many ways so as to permit an easy row of traffic.

单选题Without outside ______ China"s advertising cannot really mature and obtain a foothold in the global ads market.

单选题It is appropriate on an anniversary of the founding of a university to remind ourselves of its purposes. It is equally appropriate at such time for students to (41) why they have been chosen to attend and to consider how they can best (42) the privilege of attending. At the least you as students can hope to become (43) in subject matter which may be useful to you in later life. There is, (44) , much more to be gained. It is now that you must learn to exercise your mind sufficiently (45) learning becomes a joy and you thereby become a student for life. (46) this may require an effort of will and a period of self-discipline. Certainly it is not (47) without hard work. Teacher scan guide and encourage you, but lemming is not done passively. To learn is your (48) . There is (49) the trained mind satisfaction to be derived from exploring the ideas of others, mastering them and evaluating them. But there is (50) level of inquiry which I hope that some of you will choose. If your study takes you to the (51) of understanding of a subject and, you have reached so far, you find that you can penetrate to (52) no one has been before, you research. Commitment to a life of scholarship or research is (53) many other laudable goals. It is edifying, and it is a source of inner satisfaction even (54) other facets of life prove disappointing. I strongly (55) it.

单选题Because of its intimacy, radio is usually more than just a medium; it is______.

单选题He______his sorrow beneath a cheerful appearance.

单选题Every night she listened to her father going around the house, locking the doors and windows. She listened, the back door closed; she could hear the fastener of the kitchen window's click, and the restless pad of his feet going back to try the front door. It wasn't only the outside doors he locked; he locked the empty kitchen too. He was looking something out, but obviously it was something capable of entering into his first defenses. He raised his second line all the way up to bed. In fourteen years, she thought unhappily, the house will be his; he had paid twentyfive pounds down and the rest he was paying month by month as rent. "Of course," he was in the habit of saying, "I've improved the property." "Yes," he repeated, "I've improved the property," looking around for a nail to drive in, a weed to uproot. It was more than a sense of property; it was a sense of honesty. Some people who bought their homes through the society let them go to rack and ruin and then cleared out. She stood with her ear against the wall, a small, dark, angry, immature figure. There was no more to be heard from the other room; but in her inner ear she still heard the footsteps of a property owner, the tap-tap of a hammer, the scrape of a spade, the whistle of radiator steam, a key turning, a bolt pushed home, the little busy sounds of men building barriers. She stood planning.