The greenhouse effect is
a. a natural phenomenon that allows heat to escape the atmosphere.
b. a natural phenomenon that to maintain earth's temperature
c. the result of the differences in the angle of the sun's rays.
d. an unnatural phenomenon that causes heat energy to be radiated back into the atmosphere.

The greenhouse effect is  a natural phenomenon that allows heat to escape the atmosphere (option a).

Explanation:

The phenomenon by which certain gases, which are components of the atmosphere, retain part of the energy that the soil emits because it has been heated by solar radiation is called the greenhouse effect. It affects all planetary bodies endowed with atmosphere.

That is, the greenhouse effect is a natural phenomenon that occurs on Earth thanks to which the planet's temperature is compatible with life.

The sunlight that is absorbed by the earth's surface and returns to the atmosphere in the form of heat. There, greenhouse gases retain some of this heat and do not let it go outside; The rest escapes into space. It is this energy, which cannot escape the planet, that causes the surface temperature to rise.

When this process works naturally, the average temperature on the planet's surface is 15º C, and thanks to it, life becomes possible.

But by increasing the concentration of gases by work of man, the atmosphere retains more heat than necessary, causing the rise in temperatures, the melting of the poles, desertification, fires, storms and floods.

The greenhouse effect is  a natural phenomenon that allows heat to escape the atmosphere (option a).