Final answer:
The compound H2SO4(aq) fulfills the criteria for being both an Arrhenius acid and a Brønsted-Lowry acid as it can increase the concentration of H+ ions in solution and donate a proton, respectively.
Step-by-step explanation:
The compound in red from the reaction Mg(OH)2(aq) + H2SO4(aq) → 2H2O(l) + MgSO4(aq) that we need to identify is H2SO4(aq), sulfuric acid. According to Arrhenius theory, an acid is a compound that increases the concentration of H+ ions when dissolved in water. Since H2SO4 releases H+ ions in aqueous solution, it is considered an Arrhenius acid. Moving to the Brønsted-Lowry theory, an acid is a species that donates a proton, and since H2SO4 can donate a proton to form HSO4⁻, it is also a Brønsted-Lowry acid. Therefore, the correct choices for the given compound are Option 1: Arrhenius acid and Option 4: Brønsted-Lowry acid.