Passage Three
Over the years, new technologies have changed farming. Change in a general direction is a trend. Yet people often recognize trends only when they consider the past. Today, we look back at some trends in American agriculture. [32]In 1920, America had more than 25 million horses and mules. Most were used for farm work. [32]Around the same time, a competitor began to appear in large numbers. Tractors could turn soil, pull loads and speed harvests — and they could do it better. More tractors meant fewer horses and mules. [33]By the 1960s, the numbers of these work animals settled to where they remain today. That is about one-tenth the levels in 1920. Yet even the demand for tractors had its limits. Their numbers have been slowly decreasing since 1982. Experts say farmers can do more with less now because of new technologies. As tractors replaced horses and mules, farmers no longer needed to raise crops to feed work animals. Oats have long been food for horses and mules. In 1954, American farmers planted over sixteen million hectares of oats. By 2000, that was down to less than one million hectares. So what did the farmers do with the extra land? More and more farmers began to plant a new crop around the same time that the tractor became popular. It was the soybean. The soybean is one of the oldest plants harvested. Yet it was not planted widely in the United States until the 1920s. By the year 2000, close to 30 million hectares were planted with soybeans. [34]It is the nation's most important crop for high-protein animal feed and for vegetable oil. [35]In fact, soybeans are the second most valuable crop grown by American farmers after corn. Much of the soybean production goes to exports.

Questions 32 to 35 are based on the passage you have just heard.
32. In which year did tractors begin to appear in large numbers?
正确答案：A
解析：短文中提到，1920年，美国用于农业生产的马、骡数量有2500多万，“同时一个竞争者开始大量出现。拖拉机……”意即1920年拖拉机开始大量涌现，故A正确。
33. How many horses and mules did America have in the 1960s?
正确答案：D
解析：短文说，1920年，美国用于农业生产的马、骡数量有2500多万，此后一路减少，到20世纪60年代，数目趋于稳定，迄今没有变化。目前约有1920年的1/10。由此可计算出，20世纪60年代美国用于农业生产的马、骡牲口共250多万，故D正确。
34. What is America's most important crop for high-protein animal feed and for vegetable oil?
正确答案：B
解析：短文提到，到2000年，近3000万公顷土地种了大豆。“它是全国最重要的高蛋白动物饲料和植物油农作物。”故B正确。听短文答题时，要特别留意“语义强调之处”。本题"the nation's most important crop"显然符合此语义特征。
35. What is the most valuable crop grown by American farmers?
正确答案：A
解析：短文结尾处提到，“事实上，大豆是继玉米之后美国农民种植的第二大最有价值的农作物。”可见最有价值农作物是玉米，答案是A。答题方法与上题一样。对于文中语义强调的内容要有所辨别，最后才能按听到的问题答题。若能听记most valuable这语义要点，本题就容易了。