Answer: Option (a) is the correct answer.
Step-by-step explanation:
When we increase the concentration of substances in a chemical reaction then it means there are more number of molecules present in a reaction.
Hence, when these molecules will interact with each other then there will occur more number of collisions. As a result, kinetic energy of molecules will increase and this leads to increase in rate of chemical reaction.
Thus, we can conclude that increasing the concentration of substances in a chemical reaction will increase reaction rate.