Another Organ System that depends on mine

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

"d.) carbon dioxide and hydrogen sulfide"

i wish i could with all of them i can barley see the first one so here's the answer to the first one b