At the start of a reaction, the concentration of reactants decreases _.

Explanation

OPTION A: At the start of a reaction, the concentration of reactants decreases quickly because the reaction rate is proportional to the concentration of reactants, and the reaction rate increases as the concentration of reactants increases.OPTION B: The rate of a reaction depends on the collision of reactant molecules, and the frequency and strength of those collisions are influenced by factors such as temperature, concentration, and surface area, leading to a non-constant decrease in reactant concentration.OPTION C: Typically, reaction rates decrease with time because reactant concentrations decrease as reactants are converted to products.OPTION D: The decrease in reactant concentration at the start of a reaction is not necessarily exponential because the rate of reaction depends on various factors such as temperature, concentration, and catalysts which can cause fluctuations in the rate of decrease.