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?
正確答案：A
解析：短文中提到，1920年，美國用于農業生產的馬、騾數量有2500多萬，“同時一個競爭者開始大量出現。拖拉機……”意即1920年拖拉機開始大量涌現，故A正確。
33. How many horses and mules did America have in the 1960s?
正確答案：D
解析：短文說，1920年，美國用于農業生產的馬、騾數量有2500多萬，此后一路減少，到20世紀60年代，數目趨于穩定，迄今沒有變化。目前約有1920年的1/10。由此可計算出，20世紀60年代美國用于農業生產的馬、騾牲口共250多萬，故D正確。
34. What is America's most important crop for high-protein animal feed and for vegetable oil?
正確答案：B
解析：短文提到，到2000年，近3000萬公頃土地種了大豆。“它是全國最重要的高蛋白動物飼料和植物油農作物。”故B正確。聽短文答題時，要特別留意“語義強調之處”。本題"the nation's most important crop"顯然符合此語義特征。
35. What is the most valuable crop grown by American farmers?
正確答案：A
解析：短文結尾處提到，“事實上，大豆是繼玉米之后美國農民種植的第二大最有價值的農作物。”可見最有價值農作物是玉米，答案是A。答題方法與上題一樣。對于文中語義強調的內容要有所辨別，最后才能按聽到的問題答題。若能聽記most valuable這語義要點，本題就容易了。