Condition 1: Aromaticity Criteria. A compound is aromatic if it adheres to Hückel's rule: a planar ring structure with \( 4n + 2 \) π-electrons, where \(n\) is any non-negative integer.
Condition 2: Individual Compound Evaluation. - (A) Not aromatic. Although it possesses 6 π-electrons, its non-planar ring disqualifies it. - (B) Aromatic. The presence of a nitrogen atom and a conjugated system confirms its aromaticity. - (C) Aromatic. Features a 6-membered ring with alternating single and double bonds, meeting aromaticity requirements with 6 π-electrons. - (D) Aromatic. Exhibits a conjugated system and satisfies aromaticity criteria with 6 π-electrons.
Condition 3: Determination. Therefore, compounds (B), (C), and (D) are aromatic. The correct choice is (3).
Final Determination: \[ \boxed{\text{(3) B, C \& D}} \]
