Choose the answers you think fit best according to the text.
In 1928, Thomas Midgley, a scientist and engineer in America, found a way to use chlorofluorcarbons (CFCs) as a refrigerant. They proved to be a valuable compound, stable, non-poisonous, non-corrosive, non-flammable.
Their low thermal conductivity made them ideal for coolants in refrigerators and air-conditioners. In the Second World War, CFCs were widely used as cleaning solvents and in plastic foam for food and drink containers, and the insulation of buildings.
These are the products which, doubling in output every ten years, have contributed to the destruction of the ozone layer, the thin veil in the stratosphere which protects animals and plants from disease and, possibly, extinction.
Other man-made chemicals, apart from CFCs, are eating ozone molecules. Among them are halon gases used in fire extinguishers, aerosols, and refrigerators, and two compounds widely used as solvents: methyl chloroform and carbon tetrachloride. Their combined reaction on the ozone layer is devastating, allowing ultraviolet rays from the sun, known as UV-Bs, to bombard the earth.
UV-Bs cause skin cancer. Medical journals in Australia say two-thirds of the population alive today will develop some form of skin cancer. More than 250,000 of the continent's 16 million inhabitants will develop the deadliest of all, malignant melanoma.
UV-Bs can damage the immune system and leave you open to infectious diseases. They damage your eyes, burning the cornea, injuring the retina and generating cataracts. In southern Chile, blindness has begun to strike humans, sheep, rabbits and horses. The radiation kills off the plankton on which larger sea creatures depend, and in southern Chile a 12 per cent reduction in plankton has been measured.
The scientists who know about the ozone layer are worried. They give three reasons for their pessimism:
1. ozone depletion is now general over the globe, and occurring twice as fast as had been predicted: according to reports, in the first two months of this year, parts of the ozone layer shrank by 20 per cent, and levels of chlorine, the ozone-eating chemical, were 70 times higher than normal;
2. depletion is now being caused by the CFCs released in the mid-1970s, and so the chemicals being released now will endanger our children;
3. no one knows what the cumulative effects of the depletion of the ozone layer will be, but they do know that things from now on are going to change very quickly indeed.
1. Which title would best suit the passage?
A. CFCs: from Coolers to Cancers
B. The Ozone Layer
C. UV-B and Skin Cancer
D. Worries about the Ozone Layer
2. As CFCs are non-corrosive, they don't
A. poison food.
B. cause explosions.
C. eat metals.
D. damage plastics.
3. CFCs were used in drink containers because they
A. are easily moulded.
B. are light-weight
C. don't conduct heat.
D. are stable compounds.
4. How rapidly was the use of CFCs increasing?
A. Doubling every decade.
B. Doubling every year.
C. Twice as much each year.
D. Ten per cent every year.
5. A solvent is used in
6. "Bombard" is a word normally used with reference to
A. artillery fire.
B. heavyweight boxing.
C. solar radiation.
D. laser technology.
7. The opposite of "malignant" is
8. According to the text, in southern Chile, as a result of UV-B
A. fish stocks are falling.
B. fish are going blind.
C. fish are subject to disease.
D. fish food has been depleted.
9. Our children are in danger because
A. CFCs take time to attack the ozone layer.
B. CFCs are used more than ever.
C. CFCs are cumulative.
D. chlorine levels are rising.