The correct answer is (d) All of the above.
Explanation: While the greenhouse effect is a natural phenomenon, the significant increase in greenhouse gases due to human activities, leading to global warming and ozone depletion, are considered relatively recent environmental problems that have become more prominent in the last few centuries, particularly since the Industrial Revolution.
Key points about each option:
Ozone layer depletion:
Caused primarily by the release of chlorofluorocarbons (CFCs) from human activities, leading to a decrease in the ozone layer’s ability to protect the Earth from harmful UV radiation.
Greenhouse effect:
A natural process where certain gases in the atmosphere trap heat, but enhanced by increased greenhouse gas emissions from human activities, causing the Earth’s temperature to rise.
Global warming:
A specific term referring to the long-term increase in the average global temperature of the Earth’s atmosphere, primarily caused by the enhanced greenhouse effect.