Magnetic Effects of Current and Magnetism: JEE Main 2025 Physics question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: If Oxygen ion ($\mathrm{O^{-2}}$) and Hydrogen ion ($\mathrm{H^+}$) 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