For Soluble salts, which acid-base focus answer best supports this Unit 4.4 objective: Write balanced symbol equations for soluble salt preparation when formulae are supplied?

The correct option is Mg + 2HNO3 → Mg(NO3)2 + H2 - correct acid-base focus for soluble salt.

The correct option is Mg + 2HNO3 → Mg(NO3)2 + H2 - correct acid-base focus for soluble salt. Mg + 2HNO3 → Mg(NO3)2 + H2 - correct acid-base focus for soluble salt is correct because it directly supports the approved learning objective to write balanced symbol equations for soluble salt preparation when formulae are supplied. This acid-base focus variant asks students to separate soluble salt from similar Unit 4.4 chemical-change ideas. The reasoning belongs to Soluble salts within Reactions of acids, so it should not be confused with nearby ideas about acids, alkalis, bases, oxidation, reduction, displacement, reactivity, electrolysis, electrodes, ions, pH, or salt preparation unless those are named in the objective. Use the focus term soluble salt to keep the answer aligned with AQA GCSE Chemistry 8462 Unit 4.4 Chemical changes. Keep acid, alkali and base distinct; keep oxidation and reduction distinct; do not mix reduction with displacement; keep electrolysis separate from electroplating; distinguish anode from cathode, positive ions from negative ions, oxidation state from ionic charge, and strong acid from concentrated acid. The other options are weaker because they either use the wrong reaction type, wrong ion, wrong electrode, wrong acid-base distinction, vague wording, or the wrong chemical-change context.