Concept:Ionisation of air depends on the charge, mass and speed of the radiation: alpha particles cause the most ionisation, beta particles cause moderate ionisation, and gamma rays cause the least ionisation.
Explanation:Gamma rays are neutral electromagnetic waves, so they interact weakly with air and have the lowest ionising power.
Beta particles are fast electrons or positrons with a small charge and mass, so their ionising power is between gamma and alpha.
Alpha particles carry a double positive charge and have a relatively large mass; they are slow but cause many ionisations in a very short distance.
Therefore, the increasing order of ionisation of air is
γ<β<α.
Using the given Roman numeral labels, this means
II<III<I.
Answer:Option C:
II<III<I.