2 mL each of concentrated HCl, HNO3 and a mixture of concentrated HCl and concentrated HNO3 in the ratio of 3: 1 were taken in test tubes labelled as A, B and C. A small piece of metal was put in each test tube. No change occurred in test tubes A and B but the metal got dissolved in test tube C respectively. The metal could be
Al
Au
Cu
Pt

Correct Answer: (b) Au

Explanation: Solution C is a mixture of Concentrated HCl and Concentrated HNO₃ which is called aqua regia. Aqua Regia dissolves gold.