Some single-celled organisms make copies of themselves through mitosis. which decribes the function of the cell cycle in such single-celled organisms? a)reproductionb)repairc)growthd)pro tection

Its not d because that's not even part of it. But your answer is A

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme