单选题 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.

单选题 According to the passage, the root cause for weather changes on the earth is ______.
A．the atmosphere surrounding the earth
B．water from oceans and lakes
C．energy from the sun
D．greenhouse gases in the sky

单选题 Only a small part of the sun's energy reaches the earth's surface because most of it is ______.
A．absorbed by the clouds in the lower atmosphere
B．reflected by the gases in the upper atmosphere
C．lost in the upper and lower atmosphere
D．used to evaporate water from the oceans and lakes

单选题 We learn from the passage that ______.
A．all living things on the earth depend on the sun for their food
B．a forest looks dark in winter because it absorbs solar energy
C．only 0.023 of the energy from the sun is made use of on the earth
D．greenhouse gases allow heat energy to escape from the earth's surface