The increasing order (lowest first) for the values of $e/m$ (charge/mass) for electron ($e$), proton ($p$), neutron ($n$) and alpha particle ($\alpha$) is:

The correct option is D $n$, $\alpha$, $p$, $e$
Charge/mass ratio is inversely proportional to the mass and hence electron with lightest mass has the greatest charge/mass ratio followed by protons, alpha particles and neutrons.