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  3. We experience different forms of the sun’ s energy every day. The sun is the major source of energy for our planet. It causes th

We experience different forms of the sun’ s energy every day. The sun is the major source of energy for our planet. It causes th

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问题     We experience different forms of the sun’ s energy every day. The sun is the major source of energy for our planet. It causes the evaporation(蒸发)of water from the oceans and lakes. Sunlight also provides the energy used by green plants to make their own food.
    Much of the energy that comes from the sun never reaches the earth’ s surface. It is either reflected or absorbed by the gases in the upper atmosphere. Of the energy that reaches the lower atmosphere , 30% is reflected by clouds or the earth’ s surface. The remaining 70% warms the surface of the planet, causes water to evaporate, and provides energy for the water cycle and weather. Only a tiny part, approximately 0.023% , is actually used by green plants to produce food.
    Many gases found in the atmosphere actually reflect heat energy escaping from the earth’ s surface back to the earth. These gases act like the glass of a greenhouse in that they allow energy from the sun to enter but prevent energy from leaving. They are therefore called greenhouse gases.
    When sunlight strikes an object, some of the energy is absorbed and some is reflected. The amount reflected depends on the surface. Dark-colored surfaces, such as dark soil or forest, absorb more energy.
According to the passage, the root cause for weather changes on the earth is ______.
选项 A、the atmosphere surrounding the earth
B、water from oceans and lakes
C、energy from the sun
D、greenhouse gases in the sky
答案C
解析 事实细节题。由文章第二段The remaining 70％warms…and provides energy for thewater cycle and weather．即“剩余的70％给地球表面提供热，促进水蒸发，给水循环和大气循环提供能量”一句可知答案。故选C。
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