4) Why is the natural greenhouse effect of Earth a cause for concern now?
A) Greenhouse gases act as natural insulators and prevent the heat of the Sun from reaching Earth.
B) Greenhouse gases destroy the ozone layer, which acts as natural insulation against ultraviolet radiation from the Sun.
The rise in the amount of greenhouse gases has resulted in global warming, because more heat gets trapped in the atmosphere.
D) The rise in the amount of greenhouse gases has reduced the amount of oxygen in the air, decreasing the breathable air on Earth.