When Columbus reached the New World, corn was the most widely grown plant in the Americas. This plant s range extended from what is now southern Canada to lower South America. At that time some tribes cultivated it at sea level, others at elevation of more than 11,000 feet. "Columbus had no way of knowing that corn was far more valuable than the spices (香料) and gold he had hoped to find." said Frances B. King, a professor at a university of Pittsburgh. Through human intervention, this plant has developed into several hundred races, or varieties. Their heights vary from 2 to 12 feet, and their maturity ranges from little more than 2 months to almost a year. Their ears vary not only in color, but also in size. Unlike other cereals (谷类), corn bears little resemblance to its wild ancestors. In fact, it differs from the appearance of its immediate ancestors more than any other cultivated plant known. From humble origins as a lowland grass, corn developed into the western world s important grain. As its high yields allowed communities to grow far beyond what early agriculture could feed, most scientists viewed corn as having largely fueled pre-Columbian growth and civilization. Now, new findings are greatly altering researchers′notions about the time when corn revolution occurred. New dates for its emergence from Mesoamenrica do not support the widely held view. The evidence now suggests that the signs of corn in Americas can date back 5,500 years at least. 1. The first paragraph states that corn _____. A. was mainly grown at sea level B. was not grown below the elevation of 11,000 feet C. was widely grown in Canada only D. spread throughout Americas 2. The second paragraph implies that _____. A. the purpose of Columbus′exploration was to discover corn B. corn was one of Columbus′discoveries, but more precious than anything else C. Columbus knew corn so well that he brought back to Europe at once D. corn was the only Columbus′discovery that was remembered 3. According to the passage, some varieties of corn can _____. A. ripen little more than 2 months B. last little more than 2 months C. stay fresh for almost a year D. stay alive from 2 months to almost a year 4. Corn helped the early communities to grow because _____. A. it was easy to digest B. it had a lot of varieties C. it could produce high yields D. it could last long 5. The widely held view was challenged by _____. A. a new revolution B. new findings about corn C. the signs of corn 5,500 years ago D. new dates for communities′emergence 百考试题编辑竭诚为你提供全面的优质考试资料！