单项选择题

In 1969, the National Wildlife Federation began to record an index of environmental quality which measures progress or decline in 7 environmental areas. The index represents the judgment of environmental protection experts and advocates influenced by very high standards of environmental quality. In 1979, the Federation reported the trends of the last 10 years.
Wildlife: During the last 10 years, wildlife protection became a much more popular issuE.Legal challenges forced the Forest Service to take more effort in protecting wildlife from the effects of logging; the Bureau of Land Management has been forced to cut down on off-road vehicle use to decrease habitat destruction. In the courts, the Alaska pipeline was not stopped, but it was altered so migrating caribou could cross it; a plan to dig a canal across Florida was halteD.Overall results showed gains for wild turkeys, Atlantic salmon, deer, alligators, whooping cranes, eagles, and bighorn sheep.
Air: 'The air is somewhat cleaner, but most changes,' concedes one U.S. official, 'have just kept things from getting worsE.' The 1970 federal air pollution standards have resulted in nearly 7,000 monitoring stations and the compliance of nearly 90 percent of all major U. S. factories. Unfortunately, the newer cars have been producing more smog-causing pollution than expecteD.The EPA reports that, of the nation's 105 largest urban areas, only Honolulu has really clean air, and smog is a serious problem in almost one fourth of the country's 3,200 counties. Carbon monoxide pollution has declined at a rate of 6 % annually since 1970 and levels of other automobile pollutants have droppeD.
Minerals: The nation increased its dependence on foreign countries for raw materials during the last 10 years, but it did make some small moves to solving its problems. The rate of increase of energy use declined slightly, with industry achieving important energy savings while gasoline consumption by motorists continued to edge up. Congress tended to hold back significant energy legislation, but it did establish the new Department of Energy in 1977. 'Soft' energy alternatives, particularly solar energy, were increasingly explored, as nuclear power and coal encountered great problems.
Water: The EPA gave local governments almost ＄19 billion to build modern sewage- treatment facilities, but two-thirds of all U.S. cities are still dumping partially treated sewage into adjacent waters every day. The value of such treatment plants has been questioned as contamination from rain runoff, which is unaffected by such plants and may be uncontrollable, has come to be seen as responsible for more than half of all water pollution. About 3,600 of the nation's 4,000 major industrial polluters are meeting their cleanup deadlines, but toxic substances are still a tough challenge, with more than 70,000 chemicals currently being used for commercial purposes in the U. S..
Forests: The problem of increasing wood production to meet growing demand continueD.But small private wood lots and lands owned by the timber companies themselves are replacing national forests as the source of lumber. Water conservation, recreational, and wildlife values remain in conflict with commercial demands although a new balance is being struck with laws regulating clear-cutting, logging roads, and streamside cutting. Pesticide use is more restricted in national forests now and lumber yields have been increasing with the use of hybrid trees and the reduction of wastes in the forests and at the mill.
Soil: The pressure on soil increased with 900 million more mouths to feed worldwide than 10 years ago and with a dramatic turnabout in population trends that has led to a migration to rural and semirural areas. Protective grassland has been lost to agriculture, and the U.S. has increased its exports to ＄25 billion worth of food annually. New highways, reservoirs, subdivisions, shopping ce
A.solar energy
B.wind
C.natural gas
D.gasoline