Answer: C. Acidified \(\text{KMnO}_4\) (potassium manganate(VII)) is a strong oxidising agent; aqueous potassium iodide (KI) is a reducing agent commonly used to test for oxidising agents — yes, potassium iodide is a reducing agent because the iodide ion \(\text{I}^{-}\) is readily oxidised to brown iodine \(\text{I}_2\).
Statement 1: aqueous KI tests for oxidising agents — correct.
Statement 2: when potassium iodide is oxidised, the colour change is colourless \(\text{I}^{-}\) to brown \(\text{I}_2\). So the colour change is colourless → brown, not brown → colourless. Wrong.
Statement 3: acidified KMnO₄ tests for reducing agents — correct (a reducing agent would decolourise it, changing the purple solution to colourless).
Statement 4: when KMnO₄ is reduced, purple \(\text{MnO}_4^{-}\) becomes nearly colourless \(\text{Mn}^{2+}\). Correct.
1, 3 and 4 correct → C.
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