Adecrease in the concentration of reactants causes the rate of the reaction to slow. a. complete b. incomplete c. forward d. reverse

The correct answer is a Forward reaction to slow.
According to Le Chatelier's principle as the reactant decrease so the reaction should go leftward and this is called backward or reverse reaction so the reverse reaction will be fast to achieve equilibrium and the forward reaction will be slow.

It idk haha what are we doing?

They make up examples of physical properties