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a catalyst is a chemical that increases the rate of a chemical reaction without itself being changed by the reaction. the fact that they aren't changed by participating in a reaction distinguishes catalysts from substrates, which are the reactants on which catalysts work. enzymes catalyze biochemical reactions.
an ionic compound consists of a metal and a non-metal.
oxygen and fluorine are non-metals.
sodium and aluminium are non-metals.
calcium is a metal and chlorine is a non-metal.
nitrogen and sulfur are non-metals.
thus, the answer is c.