Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R .
Assertion A : If oxygen ion \(\left(\mathrm{O}^{-2}\right)\) and Hydrogen ion \(\left(\mathrm{H}^{+}\right)\)enter normal to the magnetic field with equal momentum, then the path of \(\mathrm{O}^{-2}\) ion has a smaller curvature than that of \(\mathrm{H}^{+}\).
Reason R : A proton with same linear momentum as an electron will form a path of smaller radius of curvature on entering a uniform magnetic field perpendicularly.
In the light of the above statements, choose the correct answer from the options given below :

1. A \(\mathrm{A}\) is true but \(\mathrm{R}\) is false.
2. B Both \(\mathrm{A}\) and \(\mathrm{R}\) are true but \(\mathrm{R}\) is NOT the correct explanation of \(\mathrm{A}\).
3. C \(\mathrm{A}\) is false but \(\mathrm{R}\) is true.
4. D Both \(\mathrm{A}\) and \(\mathrm{R}\) are true and \(\mathrm{R}\) is the correct explanation of \(\mathrm{A}\).