A neutron, a proton, an electron and an alpha particle enter a region of constant magnetic field with equal velocities. The magnetic field is along the inward normal to the plane of the paper. The tracks of the particles are lebelled in Fig. The electron follow track......... and the alpha particle follow track..........

Explanation

Path `C` is undeviated. Therefore it is of neutron's path. From Fleming's left hand rule magnitude force on positive charge will be leftwards and on negativve charge is rightwads. Therefore, tack `D` is of electron. Among `A` and `B` one of proton and other of `alpha-particle`.
Further, `r=(mv)/(Bq) or rpropm/q`
`Since, (m/q)gt(m/q)_P`
`:. r_(alpha)gtr_P`
or track `B` is of `alpha` particle.