Given below are two statements. One is labelled as
Assertion $\mathrm{A}$ and the other is labelled as Reason $\mathrm{R}$.
Assertion $\mathrm{A}$ : The first ionization enthalpy for oxygen is lower than that of nitrogen.

Reason $\mathrm{R}$ : The four electrons in $2\mathrm{p}$ orbitals of oxygen experience more electron-electron repulsion.

In the light of the above statements, choose the correct answer from the options given below.

• Correct answer
  A

  Both $\mathrm{A}$ and $\mathrm{R}$ are correct and $\mathrm{R}$ is the correct explanation of $\mathrm{A}$.
• B

  Both $\mathrm{A}$ and $\mathrm{R}$ are correct but $\mathrm{R}$ is NOT the correct explanation of $\mathrm{A}$.
• C

  $\mathrm{A}$ is correct but $\mathrm{R}$ is not correct.
   
• D

  $\mathrm{A}$ is not correct but $\mathrm{R}$ is correct

Hence, the correct answer is option: 'A'.