Ammonia undergoes neutralisation as a base reacting with an acid

Steps:

• Aqueous ammonia (NH₃) acts as a base, accepting protons.
• It reacts with phosphoric acid (H₃PO₄) or a phosphate source to form ammonium phosphate ((NH₄)₃PO₄).
• This acid-base reaction produces a salt, characteristic of neutralisation.
• No evidence of burning, electron transfer, or insoluble product formation.

Why B is correct:

• Neutralisation is the reaction of an acid and base to form a salt and water, as in NH₃ + H₃PO₄ → (NH₄)₃PO₄ (balanced appropriately).

Why the others are wrong:

• A: Combustion requires oxygen and produces heat/flame, not a salt like ammonium phosphate.
• C: Oxidation involves electron loss or gain, unrelated to salt formation here.
• D: Precipitation forms an insoluble solid from solution, but ammonium phosphate is typically soluble.

Final answer: B