Answer: A. burning fossil fuels
B. metamorphism of limestone
C. volcanism
G. animal respiration
Explanation:
The carbon cycle is a biogeochemical cycle. In this, the carbon is exchanged among different spheres of the earth atmosphere, biosphere, geosphere, hydrosphere and pedosphere on planet Earth.
Burning of fossil fuels: The fossil fuels when burn releases carbon chemicals in the form of gases such as carbon dioxide and carbon monoxide.
Metamorphism of limestone: The metamorphism of limestone released carbon dioxide gas to the atmosphere.
Volcanism: Volcanism is an act of emergence of hot magma under the surface of the earth. Along with magma, the hot gases like carbon dioxide and carbon monoxide are also released which contribute to the carbon cycle.
Animal respiration: The animals when respire release carbon dioxide to the atmosphere as a metabolic byproduct.
