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46、 The harm radiation has done to the Apollo crew members________．
A．is insignificant
B．is enormous
C．seems overestimated
D．remains unknown


47、 It can be inferred from the passage that________．
A．astronauts will have deformed children of grandchildren
B．radiation is not a threat to well protection space explorers
C．the Apollo mission was very successful
D．protection from space radiation is no easy job

48、The agricultural revolution in the nineteenth century involved two things：the invention oflabor-saving machinery and the development of scientific agriculture．Labor．saving machinerynaturally appeared first where labor was SCarCe．“In Europe”，said Thomas Jefferson，“the ob．ject is to make the most of their land，labor being abundant；here it is to make the most of ourlabor，land being abundant．”It Was in America，therefore，that the great advances in nine-teenth-century agricultural machinery first came．At the opening of the century，with the excep-tion of a crude plow，farmers could have carried practically all of the existing agricultural imple-ments(农具)on their backs；by 1860，most of the machinery in use today had been designedin an early form．The most important of the early inventions was the iron plow．As early as 1790 Ch'arles Newbold of New Jersey had been working on the idea of a cast-iron plow and spent hisentire fortune in introducing his invention．The farmers，however，would have none of it，clai-ming that the iron poisoned the soil and made the weeds grow．Nevertheless，many people devot-ed their attention to the plow，until in 1869 James Oliver of South Bend，Indiana，turned out thefirst chilled—steel(冷淬钢)plow．
根据以上内容，回答48-67题。
What is the main topic of the passage?
A．The need for agricultural advances to help feed a growing population．
B．The development of safer machines demanded by the labor movement．
C．Machinery that contributed to the agricultural revolution．
D．New Jersey as a leader in the agricultural revolution．


49、 The expression“make the most of”in Line 4 is closest in meaning to which of the following?
A．Get the best yield from．
B．Raise the price of．
C．Exaggerate the worth of．
D．Earn a living on．


50、 What point is the author making by stating that farmers could carry nearly all their tools on their backs?
A．Farmers had few tools before the agricultural revolutions．
B．Americans were traditionally self-reliant．
C．Life on the farm was extremely difficult．
D．New tools were designed to the portable．


51、 Which of the following can be inferred from what Thomas Jefferson said?
A．Europe Was changing more quickly than America．
B．Europe had greater need of farm machinery than America did．
C．America was finally running out of good farmland．
D．There was a shortage of workers on American farms．

52、Even plants can run a fever，especially when they’re under attack by insects or disease．But unlike humans，plants Can have their temperature taken from 3,000 feet away—straightup．A decade ago，adapting the infrared(红外线)scanning technology developed for militarypurposes and other satellites，physicist Stephen Paley came up with a quick way to take thetemperature of crops to determine which ones are under stress．The goal was to let farmers pre-cisely target pesticide(杀虫剂)spraying rather than rain poison on a whole field，which in-variably includes plants that don’t have pest(害虫)problems．
　　Even better．Paley’s Remote Scanning Services Company could detect crop problems be-fore they became visible to the eye．Mounted on a plane flown at 3，000 feet at night，an infra-red scanner measured the heat emitted by crops．The data were transformed into a color-codemap showing where plants were running“fevers”．Farmers could then spot-spray，using 50 to70 percent less pesticide than they otherwise would．
　　The bad news is that Paley's company closed down in 1984，after only three years．Farm,ers resisted the new technology and long-term backers were hard to find．But with the　renewedconcem about pesticides on produce，and refinements in infrared scanning，Paley hopes to getback into operation．Agriculture experts have no doubt the technology works．“This techniquecan be used on 75 percent of agricultural land in the United States"，says George Oerther ofTexas A&M．Ray Jackson，who recently retired from the Department of Agricuhrue，thinks re-mote infrared crop scanning could be adopted by the end of the decade．But only if Paley findsthe financial backing which he failed to obtain 10 years ago．
根据以上内容，回答52-71题。
In order to apply pesticide spraying precisely，we call use infrared scanning to _________.
A．locate the problem areas
B．drew a color-coded map
C．measure the size of the affected area
D．estimate the damage to the crops


53、 Farmers can save a considerable amount of pesticide by_________．
A．transforming poisoned rain
B．consuhing infrared scanning experts
C．resorting to spot-spraying
D．detecting crop problems at an early date


54、 Plants will emit an increased amount of heat when they are_________
A．sprayed with pesticides
B．in pour physical condition
C．facing an infrared scanner
D．exposed to excessive sun rays


55、 The application of infrared scanning technolgy to agriculture met with some difficul-ties due to_________．
A．the lack of official support
B．its hi．gh cost
C．its failure to help increase production
D．the lack of financial support