Question

which is one factor that adds to the greenhouse effect?
a decrease in the amount of dust in the atmosphere
a decrease in the amount of water on earths surface
an increase in gases in the atmosphere that absorb heat
an increase in the amount of solar radiation that reflects into space

Explanation:

The greenhouse effect is caused by greenhouse gases (like carbon dioxide, methane) in the atmosphere. These gases absorb and trap heat. A decrease in dust (which can reflect sunlight) would not add to the greenhouse effect. A decrease in surface water doesn't directly relate to heat - trapping. An increase in solar radiation reflection would cool the planet. But an increase in heat - absorbing gases (greenhouse gases) directly enhances the greenhouse effect as they trap more heat in the atmosphere.

Answer:

an increase in gases in the atmosphere that absorb heat