【正文】 before paragraph 1 or after paragraph 4 50. The best title for this passage might be ______. A． Dogs may smell cancer B． Why dogs can smell cancer C． A Study on dogs’ special ability D． A study on breast cancer 51. Dogs can smell cancer because ____________. A． they can detect faster than man B． their sense of smell is very sensitive C． dogs metabolize the food slowly D． patients give off bad smell 52. People can know from the passage _________. A． all dogs can be used to smell cancer B． it’ s not easy to find out cancer in the early stage C． most of the research experiments are successful D． dogs detect cancer by breathing and feeling D In the second half of each year, many powerful storms are born in the tropical Atlantic and Caribbean seas. Of these, only about a half a dozen generate the strong, circling winds of 75 miles per hour or more that give them hurricane status, and several usually make their way to the coast. There they cause millions of dollars of damage, and bring death to large numbers of people. The great storms that hit the coast start as innocent circling disturbances hundreds even thousands of miles out to sea. As they travel aimlessly over water warmed by the summer sun, they are carried westward by the trade winds. When conditions are just right, warm, moist air flows in at the bottom of such a disturbance, moves upward through it and es out at the top. In the process, the moisture in this warm air produces rain, and with it the heat that is converted to energy in the form of strong winds. As the heat increases, the young hurricane begins to swirl in a counterclockwise motion. The average life of a hurricane is only about nine days, but it contains almost more power than we can imagine. The energy in the heat released by a hurricane’s rainfall in a single day would satisfy the entire electrical needs of the United States for more than six months. Water, not wind, is the main source of death and destruction in a hurricane. A typical hurricane brings 6 to 12 inch downpours resulting in sudden floods. Worst of all is the powerful movement of the sea, the mountains of water moving toward the lowpressure hurricane center. The water level rises as much as 15 feet above normal as it moves toward shore. 53. When is an ordinary tropical storm called a hurricane? A. When it begins in the Atlantic and Caribbean seas. B. When it hits he coastline. C. When it is more than 75 mils wide. D. When its winds reach 75 miles per hour. 54. What is the worst thing about hurricane? A. The destructive effects of water. B. The heat they release. C. That they last about nine days on the average. D. Their strong winds. 55. The counterclockwise swirling of the hurricane is brought about by . the lowpressure area in the center of the storm B. the force of waves of water. C. the trade winds D. the increasing heat 56. Apparently the word “downpour” in the fourth paragraph means . A. heavy rainfall B. dangerous waves C. the progress of water to the hurricane center D. the increasing heat E Peaceful Use of Space Resources Drives China’ s Space Program China’s successful launch of its second manned spacecraft Shenzhou 6 has drawn worldwide applause. It has bee the third nation in the world capable of putting men into space. It is widely believed home abroad that the latest progress made by China will surely improve national cohesiveness(內(nèi)聚性 ) and make the country’s billion people more confident in their future in terms of social and economic progress. However, some people in and outside China describe China’s manned space program as a prestige project which yields little economic benefit. They argue that billions of US dollars spent on the decadeold space program may be better used for poverty relief and education as millions of Chinese still have a poor living and many children cannot afford basic schooling. However, mankind does need to make use of space resources for sustainable human development. Space technology has bee increasingly important for the exploration and peaceful use of space resources due to the shrinking reserve of natural resources on the Earth. Lunar reserve of isotope helium 3 is sufficient for human need for about 10,000 years, which is attractive to the mankind being troubled by high oil prices and limited oil reserve. China has benefited from the dividend of its investment in space sector, Space technology has bee an indispensable part of people’s daily life, such as weather forecast, telemunications, disaster reduction, and resources prospecting. Striving hard to feed its billion people and more in the future, China has been developing improved species of crops on the basis of space technology, mostly through recoverable satellites and spacecraft. Information obtained from Shenzhou3 and Shenzhou4 in Earth observation has been used for maritime(海上的 ) pollution control and desertification(沙漠化 ) control projects, which is useful for China and other parts