Step 1: The hybridisation of central atoms in XeF6 and IF7 is sp3d2. Both have six electron pairs around the central atom.
Step 2: The other options have different hybridisations due to the number of bonding pairs and lone pairs on the central atom.
Resonance in X$_2$Y can be represented as
The enthalpy of formation of X$_2$Y is 80 kJ mol$^{-1}$, and the magnitude of resonance energy of X$_2$Y is: