Q.Which of the following has highest bond energy ?

Catenation is the ability of an element's atoms to link to one another via covalent bonds, forming long chains, branches or rings; carbon catenates far more extensively than any other element because its C–C single bond (348 kJ/mol) is unusually strong and its small size allows good orbital overlap. Down Group 14, catenation ability falls off sharply as atoms get larger and bond enthalpies drop: $C \gg Si > Ge \approx Sn$ (bond enthalpies 348, 297, 260, 240 kJ/mol respectively), and lead shows essentially no catenation at all. Carbon's second unique ability is forming genuine $p\pi$–$p\pi$ multiple bonds — with itself (as in $C=C$, $C \equiv C$) and with other small, highly electronegative atoms (as in $C=O$, $C=S$, $C \equiv N$) — because its 2p orbitals are compact enough to achieve efficient sideways overlap. The heavier Group 14 elements cannot form comparable $\pi$ bonds because their valence p orbitals are too large and diffuse for effective overlap. It is the COMBINATION of strong catenation and $\pi$-bond formation that lets carbon build the very different bonded architectures seen in its allotropes — the 3-D $s …