The correct answer is $\boxed{\text{C}}$. Silver (Ag) is a noble metal and does not react with dilute hydrochloric acid (HCl). The other metals, zinc (Zn), iron (Fe), and calcium (Ca), are all active metals and will react with HCl to produce hydrogen gas.
Zinc reacts with HCl to produce zinc chloride and hydrogen gas:
$$Zn + 2HCl \to ZnCl_2 + H_2$$
Iron reacts with HCl to produce iron chloride and hydrogen gas:
$$Fe + 2HCl \to FeCl_2 + H_2$$
Calcium reacts with HCl to produce calcium chloride and hydrogen gas:
$$Ca + 2HCl \to CaCl_2 + H_2$$
Silver does not react with HCl because it is a noble metal. Noble metals are metals that are very stable and do not react with most other elements. Silver is a good conductor of electricity and heat, and it is also used in jewelry and coins.