Assertion Reason Magnetic Field Curvature

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A :  If oxygen ion (O^–2) and Hydrogen ion (H⁺) enter normal to the magnetic field with equal  momentum, then the path of O^–2  ion has a smaller curvature than that of 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 statement, choose the correct answer from the options given below