The correct increasing order of ionisation
enthalpy of He, Li⁺, Be²⁺ is

We know that Ionisation energy increases as we move left to right in a period and decreases as we move down the group.

Now, Li and Be belongs to same group but here Li after first ionisation enthalpy loses one electron and gains He electronic configuration which is a noble gas and noble gas has stable configuration it is difficult to remove an electron from that.

Similarly Be after losing two electrons in second ionisation enthalpy gains He configuration.

Hence, the correct order of  ionisation enthalpy is${\mathrm{Be}}^{2+}<{\mathrm{Li}}^{+}<\mathrm{He}$

Hence, option(B) is the answer.