Remember Masses of Sub-Particles,
Proton = 1.6727 x 10⁻²⁴ g
Neutron = 1.6750 x 10⁻²⁴ g
Electron = 9.110 x 10⁻²⁸ g
Protons and Neutrons are almost similar in mass, while electron is much lighter ( approximately 1800 time lighter than Proton and Neutron).
Options given are,
(a) a helium nucleus with two protons and two neutrons
(b) four electrons
(c) four individual protons
Option A and C are almost in competition. But we will prefer option-A because, it contains two neutrons along with two protons as neutron is little bit heavier than proton, also, He contains two electrons too, which can be considered in situation we are having now. :)
Result:
Option-A is correct.
