The correct order of bond enthalpy (kJ mol$$^{-1}$$) is:

We need to determine the correct order of single bond enthalpies for Group 14 elements.

Known single bond enthalpies (kJ mol$$^{-1}$$):

C$$-$$C: 348 kJ/mol

Si$$-$$Si: 226 kJ/mol

Ge$$-$$Ge: 188 kJ/mol

Sn$$-$$Sn: 151 kJ/mol

Explanation:

Carbon has the strongest single bond due to effective overlap of its small 2p orbitals. As we move down Group 14, the atomic size increases, orbital overlap becomes less effective, and bond enthalpy decreases monotonically.

The correct order is:

The correct answer is Option D.