The standard free energy change and standard activation energy for four biochemical reactions are listed in the table below:

A few interpretations are given below. Between these, the most appropriate interpretation is:

a.  P, Q, R and S represent the same reaction carried out in the presence of enzyme, high temperature, absence of enzyme and low temperature, respectively. 

b. Q and S represent the similar reaction carried out at high and low temperatures, respectively.

c. R and S represent the similar reaction carried out in the presence and absence of catalyst, respectively.

d.  P and R show the same reaction carried out in the absence and presence of enzyme, respectively.