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  3. Famed for their high-elevation forests, the Appalachian Mountains sweep south from Quebec to Alabama. Highest in New England and

Famed for their high-elevation forests, the Appalachian Mountains sweep south from Quebec to Alabama. Highest in New England and

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问题     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.
According to the passage, the melting of glaciers caused some plant species to______.
选项 A、adapt to the heat
B、die out
C、grow bigger and stronger
D、move northward
答案D
解析 细节判断题。根据题干关键词the melting of glaciers与原文第二段尾句中的the climate warmedand the ice melted对应，据此定位答案。原句中的retreated northward与选项D对应。故答案为D。
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