The percentages of various gases in the atmosphere indicate that the composition of the atmosphere is controlled
A) totally by the amount and type of gases given off during volcanic eruptions.
B) totally by the composition of comets and meteors that strike Earth.
C) to a significant extent by biological processes occurring on Earth.
D) exclusively by chemical reactions between sunlight and the gases in the atmosphere.

Question

Quizplus · Accepted Answer

The percentages of various gases in the atmosphere are maintained by biological processes such as photosynthesis and respiration, as well as geological processes. While volcanic eruptions can contribute to changes in atmospheric composition, they do not control it entirely. Comets and meteors may have had some influence on the early atmosphere, but they do not have a significant impact on the composition of the modern atmosphere. Chemical reactions between sunlight and atmospheric gases, such as ozone formation, do occur, but they are not the primary factor controlling atmospheric composition.

The Percentages of Various Gases in the Atmosphere Indicate That