My impression is that you must provide the expected answer rather than a correct one that would bring you a bad mark.
So you could start by finding in the course the so-called "five factors that scientifically increase the speed of a chemical reaction" and find one that fits the question.
Among the metal properties:
- Whether it builds an oxide layer (Ta, Ti, Cr...) that protects it from etching by that particular acid;
- Whether the ionization potential or the reduction potential is big. Search for comparisons between Li, Na, K. I saw some with water, they may exist for "acids" too.