Which of the following statements is incorrect with respect to inorganic catalysts?

The figure shows the conversion of substrate into product by an enzyme. In which one of the four options are the components of the reaction labelled $a, b, c, \& \ d$ identified correctly?
$(i)$ Potential energy
$(ii)$ Transition state
$(iii)$ Activation energy with enzyme
$(iv)$ Activation energy without enzyme

What binds to the active site of an enzyme?

Which enzyme is responsible for breaking down large molecules into smaller units?

Which of the following statements is $NOT$ associated with enzymes?

At which substrate concentration does an enzyme exhibit half of its maximum velocity?