A、To restore our atmosphere. B、To stop refrigerator-use. C、To prevent people from killing insects. D、To restrict the use of some

Scientists in the United States have reported some good news about the ozone in the atmosphere. Recent findings suggest that the destruction of ozone by pollution is slowing. Ozone is a form of oxygen. Its presence above Earth protects us from radiation from the sun.
    In one study, researchers examined information gathered by NASA space agency satellites and by equipment on Earth and said the atmosphere was losing about eight percent of the ozone layer per ten- year period since the late 1970s. In the last five years, though, that rate of loss has dropped by half. The atmosphere should start to gain ozone before long. A full recovery, however, is about 50 years away, as long as the Montreal Protocol remains in place.
    That is an international treaty from 1987 to restore the ozone layer. The treaty restricts the use of a number of chemicals that destroy ozone, like chlorofiuorocarbons, or C-F-C’s. Wide use of C-F-C’s began in the 1930s. They became popular coolants in devices such as refrigerators and air conditioners. C-F-C’s remain in the atmosphere for years.
    The Montreal Protocol also restricts the use of methyl bromide, a chemical to kill insects. Farmers and shippers are the main users. Natural sources of methyl bromide include oceans and some plants. Scientists say the bromine gas it produces is 50 times more destructive to ozone than chlorine gas from C-F-C’s.