Final answer:
Increasing the concentration of reactants and enzymes leads to a higher rate of reaction because it raises the frequency of particle collisions. option d is correct.
Step-by-step explanation:
A higher concentration of reactants and enzymes increases the rate of reaction primarily because it increases the frequency of particle collisions. This is because having more particles in a given volume leads to a higher probability of collisions, and if these collisions are energetic and oriented properly, they can lead to reactions.
Moreover, with a greater concentration of enzymes, which are biological catalysts, more active sites are available for substrates to bind to, potentially speeding up reaction times.
On the other hand, it is important to clarify that simply increasing concentration does not change the activation energy required for the reaction; rather, it just means that more particles are likely to have the energy required for a successful collision. Moreover, while raising the temperature of a chemical reaction can increase the energy of particle collisions, this is not directly related to changes in concentration.