Final answer:
Copper (Cu) is the metal that does not dissolve in hydrochloric acid (HCl) among the options provided, as it is a noble metal and does not readily react with acids.
Step-by-step explanation:
The metal that does not dissolve in hydrochloric acid (HCl) among the given options - Cu, Fe, Zn, Cd - is Copper (Cu). This is because copper is considered a noble metal, which does not react with non-oxidizing acids like HCl. In contrast, metals like Iron (Fe), Zinc (Zn), and Cadmium (Cd) are reactive and will dissolve in hydrochloric acid. Zinc, for example, reacts with HCl, forming zinc chloride and hydrogen gas. Cadmium will also react to form cadmium chloride and hydrogen gas. However, noble metals such as copper remain unreactive under these conditions.