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True, Earth is a system comprised of interacting processes. Such processes include carbon cycle, water cycle, Phosphorous cycle,...

The average propensity to consume (APC) is the ratio of consumption expenditures (C) to disposable income (DI), or APC = C / DI. 

Hence, APC = consumption/income.

RNA acts as a messenger in between the DNA and ribosome as it transforms the genetic information from the DNA and as DNA is big and can't fit into the nuclear pores. 

S8 is an elemental form of sufur. In elemental form it can't be reduced or oxidized. Hence, it oxidation number is zero and thus sulfur is zerovalent here.

Most cellular activities will occur in the cytoplasm of the cell. Many metabolic pathways including glycolysis and process such as cell division occurs in the cytoplasm of the cell.