[填空题]Acid rain means the precipitation in the form of rain, snow or hail which is more acidic than normal.

[填空题]Acid rain means the precipitation in the form of rain, snow or hail which is more acidic than normal.

[单项选择]Acid rain, which is a form of air pollution, currently becomes a subject of great debate because of widespread environmental damage for which it has been blamed. It forms when oxides of sulfur (硫) and nitrogen (氮) combine with atmospheric moisture to yield sulfuric and nitric acids, which may then be carried long distances from their source before they drop in the form of rain. The pollution may also take the form of snow or fog or fall down in dry forms. In fact, although the term "acid rain" has been in use for more than a century — it is derived from atmospheric studies that were made in the region of Manchester, England — the more accurate scientific term would be "acid deposition". The dry form of such deposition is just as damaging to the environment as the liquid form.
The problem of acid rain originated with the Industrial Revolution, and it has been growing ever since. The severity of its effects has long been recognized in local settings, as exemplified by the spells of
A. acid rain has caused air pollution
B. acid rain has caused widespread environmental damage
C. acid rain has become a much-studied subject
D. acid rain travels in all directions before it rains down

[填空题]results in "Acid rain"

[单项选择] Researchers generally agree that acid rain arises primarily from the burning of coal and oil. The emissions contain oxides of nitrogen and sulfur, which can be carried hundreds of miles on the prevailing westernly winds. They eventually return to earth as dry gases and particulates and react with ground waters to form nitride or sulfuric acid. They may also be converted to the acids in the atmosphere by chemical processes that are still not fully understood. However the acids are formed, they have already been charged with a substantial list of damages. Corrosion of metal structures in windward areas of the country has been well-documented, but is a relatively minor entry on the list. Other forms of damage are far more insidious and longer-lasting. There is evidence, for example, that the acids leach heavy metals--aluminum, lead, and mercury-from the soil, which then poison plant roots and deprive them of vital nutrients. In lakes and rivers the acid alters the blood chemistry i
A. produced by air
B. emerged in the air
C. floating
D. polluting