Which of the following carbocations is the most stable?

Step-by-step solution

The stability of a carbocation is determined by factors such as resonance, hyperconjugation, and inductive effects. In option (A), the carbocation is primary and allylic, stabilized by resonance with one double bond. In option (C), the carbocation is tertiary and allylic, stabilized by resonance with one double bond and hyperconjugation. In option (D), the carbocation is tertiary but not allylic, stabilized only by hyperconjugation. In option (B), the carbocation is tertiary and is conjugated with two double bonds.