Most metals do not liberate hydrogen gas when reacting with nitric acid (HNO₃) because nitric acid is a strong oxidizing agent and oxidizes the produced hydrogen gas to water. However, highly reactive metals like Magnesium (Mg) and manganese (Mn) are exceptions. They react with very dilute and cold nitric acid to produce hydrogen gas.
The reaction with magnesium is: Mg\(_{(s)}\) + 2HNO\(_3\)(aq, very dilute) → Mg(NO\(_3\))\(_2\)\(_{(aq)}\) + H\(_2\)\(_{(g)}\)
A. Cu (Copper) is below hydrogen in the metal reactivity series and cannot displace hydrogen from any dilute acid, including dilute HNO₃.
C. Ca (Calcium) is a reactive metal and would likely behave similarly to magnesium with very dilute nitric acid, potentially liberating hydrogen. However, Mg is the most widely cited and confirmed answer for this specific question in the provided sources, often alongside Manganese.
D. Zn (Zinc) reacts with dilute nitric acid, but typically produces oxides of nitrogen (like 
N\(_2\)O or NO), not hydrogen gas (except possibly under extremely specific, very dilute and cold conditions which are less commonly referenced than Mg).
There is an explanation video available below.
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