Which of the following best describes how the energy-profile diagram of a catalysed reaction differs from that of the same reaction without a catalyst?
a) The catalysed pathway shows fewer elementary steps, because the catalyst simplifies the mechanism.
b) The catalysed pathway shifts the energy of the reactants downward, thereby lowering both ΔH and the activation energy.
c) The catalysed pathway shows the same overall enthalpy change but a lower energy for the highest transition state.
d) The catalysed pathway shows a smaller overall enthalpy change because the catalyst releases additional heat.