Carbon dioxide is returned to the atmosphere when

During respiration in plants and animals, carbon dioxide is returned to the environment.

Carbon dioxide is a dull gas with a thickness of about 60% which is higher than that of dry air. Carbon dioxide comprises of a carbon particle covalently twofold attached to two oxygen molecules. It is seen in atmosphere in traces.

When organism such as plant, animals, algae and other microorganism respires, it leads to return of carbon dioxide to the environment as it is the major compound formed due to the metabolic activity in them. Apart from this burning of fossil fuels and deforestation also act as cause of returning of carbon dioxide to the environment.

it’s lava came from an explosive eruption

the correct answer is 4) heat and pressure

metamorphic rocks arise from transformation of existing rocks types, in a process called metamorphism. during metamorphism the original rock(prolith) change into metamorphic rock by heating (150-200c) and pressure of more than 1000 bar. the original rock can be sedimentary, igneous, or existing metamorphic rock.