In the preparation of compounds of Xe, Bartlett had taken O2+PtF6- as a base compound. This is because-

1. Both Oand Xe have the same size.
2. Both O2  and Xe have the same electron gain enthalpy.
3. Both O2 and Xe have almost the same ionisation enthalpy.
4. Both Xe and O2 are gases.

Hint: Both O2 and Xe have almost the same ionisation enthalpy.
Bartlett prepared a red compound which is formulated as O2+PtF6- . Then he realised that the first ionisation enthalpy of molecular oxygen (1175 kJmol–1) was almost identical to that of xenon (1170 kJ mol–1).
The ionisation enthalpies of noble gases are the highest in their respective periods due to their stable electronic configurations.
Hence, option third is the correct answer
size of Oxygen is 48 pm, and Xenon 108 pm
Ea of Xenon = zero, 
Ea of oxygen = 141kj/mol