MC Common Acid and Alkalis

The answer is B.

If concentrated nitric acid used, both copper and silver can dissolve in hot concentrated nitric acid to give a mixture containing blue copper(II) nitrate solution and colourless silver nitrate solution. Therefore, the final colour of the solution is pale blue.
Cu(s) + 4HNO3(aq) → Cu(NO3)2­(aq) + 2H2O(l) + 2NO2(g)
Ag(s) + 2HNO3(aq) → AgNO3­(aq) + H2O(l) + NO2(g)

If dilute nitric acid used, both copper and silver can also dissolve in hot dilute nitric acid to give a mixture containing blue copper(II) nitrate solution and colourless silver nitrate solution. Therefore, the final colour of the solution is also pale blue.
3Cu(s) + 8HNO3(aq) → 3Cu(NO3)2­(aq) + 4H2O(l) + 2NO(g)
3Ag(s) + 4HNO3(aq) → 3AgNO3­(aq) + 2H2O(l) + NO(g)
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