Explain the following reactions in mechanistic terms. Show arrow pushing. The number of new C-C σ bonds formed when the polyene reacts with HBr to give the tricyclic bromide is :

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Olefins can be protonated under acidic conditions, forming electrophilic and cationic carbon atoms. Due to their nucleophilic character, olefins can also add to sites of positive charge. An H⁺ protonates the terminal trisubstituted C=C bond, yielding a tertiary cation. This is followed by three successive 6-membered ring closures, where each remaining C=C bond adds to the cationic center in a cascade. Finally, Br^- captures the tricyclic cation. This cascading mechanism, illustrated below, generates polycyclic systems through cation-π cyclization.

Answer: (B)

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