Which of the following statement is correct for isotope of carbon?

The explanation of given statements are as follows (i) Graphite is conductor of electricity because it has free valence electron which does not participate in bonding. Thus, statement (a) is correct. (ii) Diamond has a three dimensional structure in which $\mathrm{sp}^3$-hybridised C -atoms are arranged tetrahedrally. Thus, statement (b) is correct. (iii) Graphite is thermodynamically more stable than diamond and its free energy of formation is less than diamond. However, entropy of graphite is more than diamond.