Carbocation stability rises as the electron deficiency at the positive carbon is relieved by neighbouring electron-donating or delocalising influences. The benzyl cation is stabilised by resonance, since the empty p orbital overlaps with the aromatic pi system and the positive charge is delocalised onto the ortho and para ring carbons, spreading it over several atoms. The tertiary butyl cation is stabilised only by the +I effect and hyperconjugation from nine alpha hydrogens, which is significant but localised and weaker than full resonance delocalisation, so it ranks below benzyl. The isopropyl cation, being secondary, has fewer hyperconjugative and inductive contributions and is less stable still. The methyl cation has no alkyl groups to donate electrons and is the least stable of all. Because resonance dispersal over an aromatic ring outweighs purely inductive and hyperconjugative effects, the benzyl cation wins, even though the tertiary cation looks attractive at first glance. This ordering of resonance above hyperconjugation above induction matches the NCERT treatment of reactive intermediates and is a recurring theme in JEE problems on relative stability. Plausibility check: the more atoms that share the positive charge, the lower the overall energy, and resonance into the benzene ring shares the charge over the widest set of carbons, confirming the benzyl cation as the most stable of the four.