Why does an increase in temperature result in an increase in reaction rate? why does an increase in temperature result in an increase in reaction rate? a) an increase in temperature raises the activation energy which increases the reaction rate. b) an increase in temperature causes the molecules to increase in size which increases reaction rate. c) an increase in temperature decreases the concentration of reactants which increases reaction rate. d) an increase in temperature causes an increases the number of collisions which increases reaction rates.