The order of stability of the following carbocations:

Stability of carbocations depends on delocalization of charge:${\text{C}}_6{\text{H}}_5{\text{CH}}_2^{+}$ (III): Benzyl carbocation is stabilized by resonance with the benzene ring (multiple resonance structures).${\text{H}}_2\text{C}=\text{CH}-{\text{CH}}_2^{+}$ (I): Allyl carbocation is stabilized by resonance with one double bond.${\text{CH}}_3-{\text{CH}}_2-{\text{CH}}_2^{+}$ (II): Propyl carbocation (primary) is only stabilized by inductive effect and hyperconjugation.Order: III > I > II.