[originaltext] The ordinary raindrop is a mighty earthmover with sufficient

游客2023-09-12  27

问题  
The ordinary raindrop is a mighty earthmover with sufficient strength to cut rock. When rainwater collects on the surface of the ground, some of it evaporates and some of it sinks into the earth. The remainder begins to flow downhill, commencing its lengthy journey from brook to stream to lake, or to a river that will carry it to the sea.
    As water flows along the ground, it picks up sand, pebbles, even boulders. It uses them to gnaw at the sides and bottoms of its channel, gradually loosening more earth.
    By this process enormous amounts of mud and rock are moved from the land to the sea. Each year the Mississippi River carries 730 million tons of solid matter into the Gulf of Mexico.
    This constant hauling of land into the sea is lowering the United States’ average height above sea level at a rate of about one foot every 9,000 years. If erosion continues at the same rate, the United States will be worn completely down to sea level in about 23 million years.
What does erosion by water result in?

选项 A、It will rise an average of 1 foot.
B、It will be worn down an average of 1 foot.
C、It will be worn down to sea level.
D、It will lose 730 million tons of solid matter.

答案 C

解析 事实细节题 文章的最后谈到了水对陆地的巨大冲击力可以使陆地逐渐下降,因而美国将在 2300万年后完全淹没在海平面以下。
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