单选题
Famed for their high-elevation forests, the Appalachian Mountains sweep south from Quebec to Alabama. Highest in New England and North Carolina, this broad system covers more than 1,200 miles to form the rocky backbone of the eastern United States.
The Blue Ridge Mountains form a substantial part, 615 miles, of the far-reaching Appalachians. They begin as a narrow, low ridge in Pennsylvania, then slowly spread and rise until they reach the height of 5,938 feet at majestic Grandfather Mountain in North Carolina. The Blue Ridge technically includes among its major spurs the Great Smoky Mountains and the Black Mountains; Mount Mitchell, in the latter range, is at 6,684 feet the highest peak east of the Mississippi River. Like the rest of the Appalachians, these mountains were once substantially higher and bolder. Their uplift was completed some 289 million years ago, and they have been drastically eroded ever since. At one time, immense continental glaciers covered the land as far south as Pennsylvania. Although they did not spread over the Blue Ridge, plants and animals far beyond their reach became adapted to the cold. When the climate warmed and the ice melted, the cold-adapted species retreated northward, surviving in the south only at higher,
cooler elevations.
Red Spruces and Fraser firs are remnants of the Ice Age, thriving in the higher elevations of the Blue Ridge; and local belches, birches, and red oaks are typical of forests farther to the north. Sharing the high peaks is another distinctive plant community. This is the "bald"—a treeless area covered with grass, or more commonly, with broad-leaved shrubs. Often large and vigorous, the latter include huckleberries, mountain laurel, and most especially, rhododendron, an evergreen shrub that blossoms in June and creates some of the most spectacular wild gardens on Earth.
单选题
The southernmost point of the Appalachian Mountains is in ______.
单选题
Where in the passage does the author mention what has happened to the development of the mountains since they reached their highest point?
【正确答案】
B
【答案解析】[解析] 细节事实题。根据题干关键词the mountains...reached their highest point与原文第二段第五句中的their uplift was completed对应，据此定位答案，这句话其实跟问题的意思是一样的，就是说，这些山的上升已经完成了，也就是达到顶峰了，从那以后，他们就开始被剧烈地侵蚀了。故答案为B。
单选题
According to the passage, a 615-mile expanse of the Appalachians is known as ______.