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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 form. 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
A.the atmosphere surrounding the earth
B.water from oceans and lakes
C.energy from the sun
D.greenhouse gases in the sky

A.B.023%,
C.
D.
E.
According
F.the
G.water
H.energy
I.greenhouse

【参考答案】

C
解析:事实细节题。由文章第二段“the remaining 70% warms... and provide......

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Minority-owned business in the United States had unprecedented opportunities as well as new and significant risks. Civil rights activists have long argued that one of the principal reasons why Blacks and other minority groups have difficulty establishing themselves in business is that they lack access to sizable orders and subcontracts that are generated by large companies. Now Congress, in apparent agreement, has required by law that business awarded federal contracts of more than $500,000 do their best to find minority subcontractors and record their efforts to do so on forms filed with the government. Indeed, some federal and local agencies have gone so far as to set specific percentage goals for apportioning parts of public works contracts to minority enterprises.Corporate response appear to have been substantial: According to figures collected in 2003. the total of corporate contracts with minority business rose from $77 million in 1998 to $1.1 billion in 2003. The projected total of corporate contracts with minority business for the early 2004 is estimated to be over $3 billion per year with no ceasing anticipated in the next decadE.Promising as it is for minority business, this increased protection poses dangers for them, too. First, minority firms risk expanding too fast and overextending themselves financially, since most are small concerns and, unlike large business, they often need to make substantial investments in new plants, staff, equipment, and the like in order to perform. work subcontracted to them. If, thereafter, their subcontracts are for some reason reduced, such firms can face potentially crippling fixed expenses. The world of corporate purchasing can be frustrating for small entrepreneurs who get requests for elaborate formal estimates and bids. Both consume valuable time and resources, and a small company's efforts must soon result in orders, or both the morale and the financial health of the business will suffer.A second risk is that White-owned companies may seek to cash in on the increasing apportionments through formation of joint ventures with minority-owned concerns. Of course, in many instances there are legitimate reasons for joint ventures; clearly, White and minority enterprises can team up to acquire business that neither could acquire alonE.But civil rights groups and minority business owners have complained to Congress about minorities being set up as 'fronts' with White backing, rather than being accepted as full partners in legitimate joint ventures.Third, a minority enterprise that secures the business of one large corporate customer often runs the danger of becoming--and remaining dependent. Even in the best of circumstances, fierce competition from large, more established companies makes it difficult for small concerns to broaden their customer bases; when such firms have nearly guaranteed orders from a single corporate benefactor. they may truly have to struggle against serf-satisfaction arising from their current success.Why does the author say 'minority-owned business in the United States had unprecedented opportunities'?A.Because minority-owned business takes up more shares in the market.B.Because large companies generate more subcontracts.C.Because they are awarded federal contracts.D.Because the government provides favorite conditions and protection.
A.B.1
C.
D.
E.
F.
Why
G.Because
H.
B.Because
I.
C.Because
J.
D.Because