Researchers have found that increasing global temperatures will cause methane (ch4), a greenhouse gas, to be emitted at increasing rates by microorganisms found in freshwater ecosystems. what biogeochemical cycle will be most directly affected by this increase in methane
carbon cycle
hydrogeological cycle
nitrogen cycle
phosphorous cycle

The correct answer is carbon cycle.

Explanation:

In the given question it is clear that the rate of methane emission will go high because of the foreseen rise in temperature due to global warming. The biogeochemical cycle, which will get influenced directly via this will be the carbon cycle.  

Methane is a compound comprising four atoms of hydrogen and one atom of carbon. In the carbon cycle, the carbon dioxide discharged by the organisms gets captivated by the producers, and due to the increase in methane emission the absorption of carbon dioxide gets affected due to its over-presence. The carbon that is to be captivated by the producers should be present in the form of carbon dioxide.  

"d.) carbon dioxide and hydrogen sulfide"

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".