As reaction starts instantaneous rate is :

Explanation

At the start of a chemical reaction, the concentration of reactants is highest, which increases the frequency of collisions between reactant molecules. According to collision theory, this increased collision frequency results in a higher instantaneous rate of reaction compared to the average rate, which is calculated over the entire course of the reaction. Option A is correct because it accurately reflects this initial high rate due to the abundance of reactants. Options B and C are incorrect because they fail to acknowledge the increased collision frequency at the start. Option D is incorrect as it dismisses the accurate statement provided in Option A.