Balancing a chemical equation requires satisfying conservation of mass (atomic balance) and charge. The unbalanced reaction is: (\text{Al} + \text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + \text{H}_2). Aluminium sulfate contains 2 Al atoms, so 2 Al atoms are needed on the left. Each (\text{H}_2\text{SO}_4) provides one (\text{SO}_4^{2-}), and three are needed for (\text{Al}_2(\text{SO}_4)_3), so 3 (\text{H}_2\text{SO}_4) molecules are required. Balanced: (2\text{Al} + 3\text{H}_2\text{SO}_4 \rightarrow \text{Al}_2(\text{SO}_4)_3 + 3\text{H}_2). Option 1 is insufficient; only one (\text{SO}_4^{2-}) unit would be supplied, but (\text{Al}_2(\text{SO}_4)_3) needs three. Option 2 provides two sulfate units, still one short of three. Option 4 is too many and would leave one (\text{SO}_4^{2-}) unit unaccounted for, violating mass balance. This is a direct NCERT exercise on balancing equations by inspection. Plausibility check: with 3 (\text{H}_2\text{SO}_4), we have 6 H on the left, giving (3\text{H}_2) on the right — the hydrogen balance is also satisfied.