The carbocation C₆H₅-+CH-CH₃ (1-phenylethyl cation) is stabilized by the interaction of the empty p orbital with:

Solution & Explanation

Concept — A carbocation is electron-deficient: the central positive carbon is sp² with an empty p orbital. It is stabilised when nearby electron pairs (filled orbitals) can donate density into that empty p orbital. Donation always comes from FILLED orbitals into the EMPTY one. For C₆H₅–⁺CH–CH₃ (the 1-phenylethyl / benzylic cation) there are two such filled donors: (1) Resonance/conjugation: the benzene ring's filled π orbitals overlap with the empty p orbital, delocalising the positive charge onto the ortho and para ring carbons. This is the dominant stabilisation (benzylic). (2) Hyperconjugation: the filled σ (C–H) bonding orbitals of the adjacent CH₃ group overlap with the empty p orbital, donating σ electron density. Both donors — the ring π and the C–H σ — are FILLED orbitals. Why the others fail: empty orbitals (σ*, π*) have no electrons to donate, so they cannot stabilise an already electron-deficient cation; options (B), (C) and (D) all invoke empty/antibonding orbitals. Hence the empty p orbital is stabilised by filled σ and filled π orbitals — option A.