An electron and a proton are injected into a uniform magnetic field perpendicular to it with the same momentum. What is the nature of their trjaectories?

Linear momentum p=mV⇒V=pm and angular frequency ω=QB/m. Both of the particles will move along circular path. Radius of curvature, γ=Vω=pm×mQB=pQB charge Q is same for both. So option (3) is right.