# Which of the following is most stable

$(a)\;Ph_3C^+ \\ (b)\;Ph_2CH^+ \\ (c)\;PhCH_2^- \\ (d)\;Tropylium \;cation$

Greater the number of phenyl groups attached to the carbon atom bearing the positive charge, larger is the resonating structures. more stable is the carbocation.
So, $Ph_3C^+$ is correct
Hence a is the correct answer.