The high point in railroad building came with the construction of the first transcontinental system. In 1862 Congress authorized two western railroad companies to build lines from Nebraska westward and from California eastward to a meeting point，so as to complete a transcontinental crossing linking the Atlantic seaboard with the Pacific. The Government helped the railroads generously with money and land. Actual work on this project began four years later. The Central Pacific Company, starting from California, used Chinese labor, while the Union Pacific employed crews of Irish labourers. The two groups worked at remarkable speed, each trying to cover a greater distance than the other. In 1869 they met at a place called Promontory in what is now the state of Utah. Many visitors came there for the great occasion. There were joyous celebrations all over the country, with parades and the ringing of church bells to honor the great achievement.
The construction of the transcontinental railroad took_.
A. 9 years B. 7 years C. 4 years D. 3 years
D这是一道有关年代考点的细节题。根据文章：美国国会1862年授权两家铁路公司建设横贯美国 东西两岸的铁路，实际修建时间为1866年(国会授权后4年开始修建)，于1869年在犹他州的 Promontory相会。因此1869 了 1866 = 3 years,那么D为正确答案。一些考生由于不细心，未看淸实际 施工的时间应为1866年,而将其误为1862年，所以错选了 B。