First ionization enthalpy (IE1) of B, Al, Ga are 801, 577 and 579 kJ/mol respectively.
As decrease in first ionization enthalpy is much larger from B to Al. ΔIE1 of B and Al is greater than ΔIE1 of Al and Ga. So, the statement I is correct.
This is due to completely filled d-orbitals in Ga and d-electron have low screening effect to compensate the increase in nuclear charge. So, The statement II is also correct.
Hence, the correct option is B.