Which of the following is the most stable diazonium salt?
The correct option is D $$C_6H_5N_2^+X^-$$
Aliphatic amines do not give diazo compounds. The most stable diazonium salt is $$C_6H_5 N_2^+ X^-$$. Diazonium salt containing aryl group directly linked to the nitrogen atom is most stable due to resonance stabilization between the benzene nucleus and N-atom.