Which one of the following statement is incorrect in relation to ionization enthalpy?

Which one of the following statement is incorrect in relation to ionization enthalpy ?
(a) Ionization enthalpy increases for each successive electron.
(b) The greatest increase in ionization enthalpy is experienced on removal of electron from core noble gas configuration.
© End of valence electrons is marked by a big jump in ionization enthalpy.
(d) Removal of electron from orbitals bearing lower n value is easier than from orbital having higher n value.

(d) It is easier to remove an electron from orbitals bearing, higher n value than from orbital having lower n value.