The correct answer is Only (a) and (c). Explanation & Key Takeaways: • The rate of a chemical reaction is generally proportional to the concentration of reactants. This is because higher concentrations of reactants increase the frequency of collisions between molecules, leading to a higher reaction rate. • The rate of a chemical reaction increases with an increase in temperature. This is because higher temperatures provide reactant molecules with more kinetic energy, increasing the likelihood of successful collisions that lead to a reaction. Related Concepts: • Statement (b) is incorrect because the rate of reaction does not decrease with an increase in the concentration of reactants. Instead, it increases. • Statement (d) is incorrect because the rate of reaction does not decrease with an increase in temperature. Instead, it increases due to higher energy availability for the reacting molecules. • The relationship between reaction rate, concentration, and temperature is explained by the collision theory and the Arrhenius equation.