Ozone layer depletion was not noticed until 1979, while CFC’s have been around since 1920s because CFCs take time to enter the stratosphere and remain there for at least 60 years after their initial release.
Option: A
Explanation:
Ozone layer is found in stratosphere. Ozone plays a dual role in the environment. When it is in the ground surface zone it is a harmful gas but when its in the atmosphere it is a life saving layer which absorbs UV rays and protect human beings and animals from the harmful affect of poisonous gases.
Though ozone layer started depleting from 1920. But it came into notice from 1979 as CFCs take time to enter the stratosphere and remain there for at least 60 years after their initial release.
Answer:
Igneous rocks can be divided into four categories based on their chemical composition: felsic, intermediate, mafic, and ultramafic. The diagram of Bowen's reaction series (Figure 7.6) shows that differences in chemical composition correspond to differences in the types of minerals within an igneous rock.
Explanation:
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