A rapid means of long-distance transportation became a necessity for the United States as settlement spread over farther westward. The early trains were impractical curiosities,and for a long time the railroad companies met with troublesome mechanical problems. The most serious ones were the construction of rails able to bear the loadand the development of a safe,effective stopping system. Once these were solved?the railroad was established as the best means of land transportation. By I860 there were thousands of miles of railroads crossing the eastern mountain ranges and reaching westward to the Mississippi. There were also regional southern and western lines.

　　The major problems with Americans railroad system in the mid 19th century lay in.

　　A. poor quality rails and unreliable stopping systems

　　B. lack of financial support for development

　　C. limited railroad lines

　　D. lack of a transcontinental railroad

　　講解答案：

　　本題問(wèn)的是19世紀(jì)中葉美國(guó)鐵路系統(tǒng)存在的問(wèn)題。作者在第一段第三句中指出，當(dāng)時(shí)最嚴(yán)重的技術(shù)問(wèn)題是the construction of rails able to bear the road和the development of a safe,effective stopping system，所以答案為A。這個(gè)問(wèn)題與該句的比較考點(diǎn)相聯(lián)系The most serious ones。