What’s the greenhouse effect?
a. the trapping of warm air in cities
b. human caused global warming
c. the regulation of atmospheric and surface temperatures
d. the release of extra moisture from water vapor

The greenhouse effect can be referred to as the trapping of warm air in cities.

Explanation:

The structure of a greenhouse is such that the warmth and moisture inside the enclosed area get trapped. This is because the heat that penetrates through the semi-transparent walls of the greenhouse is in the form of stronger waves of shorter wavelength, and the heat that is reflected back is in the form of weaker waves of a longer wavelength that is incapable of penetrating back through the walls of the greenhouse. Same goes with the warm air trapped in the cities. The particulate matter from various pollutants present in the atmosphere traps the heat and warms the air around. Thus, the greenhouse effect can be referred to as the trapping of warm air in cities.

Answer volcanic outgassing;

Answer were lower;