Solution T is an acidic solution based on its reactions.

Steps:

• Reaction with magnesium produces hydrogen gas (H₂), characteristic of acids displacing H₂ from metals.
• Reaction with calcium carbonate produces carbon dioxide gas (CO₂), typical of acids reacting with carbonates via 2H⁺ + CaCO₃ → Ca²⁺ + H₂O + CO₂.
• Acids neutralize bases like aqueous ammonia (NH₃) to form ammonium salts, confirming option D.
• Options A and B describe basic properties, contradicting the acidic evidence; C misidentifies the gas from the carbonate reaction.

Why D is correct:

• Acids react with aqueous ammonia (a weak base) to form ammonium ions and water, e.g., HCl + NH₃ → NH₄Cl.

Why the others are wrong:

• A: Acidic solutions have more H⁺ ions than OH⁻ ions, not the reverse.
• B: pH 9 indicates a basic solution, but properties show acidity (pH < 7).
• C: Reaction with calcium carbonate produces CO₂, not hydrogen gas.

Final answer: D