题目

Deputy Agriculture Secretary Kathleen Merrigan sees an epidemic(流行病) sweeping across America's farmland. It has little to do with the usual challenges, such as flood, rising fuel prices and crop-eating insects. The country's farmers are getting older, and there are fewer people standing in line to take their place. National agricultural census（普查）figures show that the fastest-growing group of farmers is the part over 65. Merrigan is afraid the average age will be even higher when the 2012 statistics are completed. Merrigan, a former college professor, is making stops at un下列文献中最早使国人扩展了视野并介绍了西方政治制度的是 A．《海国图志》                     B． 《资政新篇》 C．《瀛环志略》                     D． 《康輶纪行》