The energy of 2s orbital of H, Li, Na, and potassium is ${\mathrm{x}}_1$, ${\mathrm{x}}_2$, ${\mathrm{x}}_3$ and ${\mathrm{x}}_4$ respectively. The correct order is

We know that, 

According to Aufbau's principle, as the atomic number increases the energies of the orbitals in the same energy level decrease.

The Aufbau principle states that an electron occupies orbitals in order from the lowest energy to highest.

The atomic number for given elements is:

For H, Z = 1

For Li, Z = 3

For Na, Z = 11

For K, Z = 19

So, the increasing atomic number (order) is $\mathrm{H}<\mathrm{Li}<\mathrm{Na}<\mathrm{K}$

Therefore, the energies of the 2s orbital for these elements are given by the order

$x_1>x_2>x_3>x_4$ (Since energies decrease when the atomic number increases).