In the middle of winter when snow is falling in many parts of the United States. Scien
tists have sounded the sun this summer. The warning: The sun’s summer time rays are more dangerous than once thought.
A team of scientists from 80 nations recently reported to the United Nations that a layer of ozone(臭氧层) in the atmosphere which protects humans from harmful levels of ultraviolet (紫外的) radiation will be thinner over the United States this summer. The thinner layer allows more ultraviolet rays from the sun to reach earth. The extra amount of ultraviolet radiation could cause an increase in the number of cases of skin cancer.
Scientists first became concerned about the ozone layer in the mid-1980s when a hole was discovered in the layer above Antarctic during the winter. The hole was caused by chemicals used in refrigerators and air conditioners. When these chemicals are sent out into the atmosphere they produce gases that destroy the ozone.
Concern about the protective ozone layer rose more recently when data (数据) from satellites and ground stations showed that ozone levels were dropping over areas other than Antarctic. Low ozone Levels were recorded in the spring and summer over the United States and over other populated areas in the world.
Although many countries have already begun stopping the use of ozone-destroying chemicals the new findings are? expected to advance the timetable for a total ban(禁止) of the chemicals.
1.The scientists have observed the ozone layer ________.
A.since 1980
B.since last winter
C.for more than 10 years
D.for about one year
2.The ozone layer in the atmosphere can ________.
A.do a lot of good to human beings in many ways
B.protect humans from diseases caused by bad weather
C.do a lot of harm to human beings in the summer time
D.protect humans from harmful levels of ultraviolet radiation
3.Scientists first found that there was a hole in the ozone layer ________.
A.above Arctic during the winter in the mid-1980
B.above Antarctic during the winter in the mid-1980
C.over somewhere in the north of the equator in 1980
D.over somewhere in the summer time in the mid-1980s
4.The damage to the ozone layer was caused by ________.
A.the changeable weather
B.ozone-destroying chemicals
C.chemicals from refrigerators
D.chemicals from air conditioners
5.Which of the following is NOT true?()
A.The use of ozone-destroying chemicals have already been stopped
B.The ozone levels in the spring and summer over the USA were low
C.More and more people have begun to protect the natural surroundings
D.Many countries have already taken measures to protect ozone layer