Statement I : Bond length in C–C > N–N > O–O
Statement II : Bond enthalpy in C–C > N–N > O–O

Left to right in a period  Atomic radius decreases
$\therefore \mathrm{size} \mathrm{of} \mathrm{C} > \mathrm{N} > \mathrm{O}$
$\therefore \mathrm{C}–\mathrm{C} > \mathrm{N}–\mathrm{N} > \mathrm{O}–\mathrm{O} \dots ..\mathrm{Bond} \mathrm{length}$
Generally
$\mathrm{Bond}\mathrm{enthalpy}\propto \frac{1}{\mathrm{Bond}\mathrm{length}}$
$\therefore \mathrm{Expected} \mathrm{trend} \mathrm{of} \mathrm{Bond} \mathrm{enthalpy}$
          C–C < N–N < O–O
But both ‘N’ and ‘O’ contain lone pairs.  Due to the repulsions between lone pairs of adjacent atoms in N–N and O–O their bond enthalpies are very low.
$\therefore \mathrm{Experimental} \mathrm{bond} \mathrm{enthalpy}$
     C–C > N–N > O–O