**Answer:**

**Introduction:**
When a metal reacts with an acid, it displaces hydrogen from the acid, resulting in the formation of a salt and the evolution of hydrogen gas. This type of reaction is known as a displacement reaction.

**Explanation:**
Among the given options, the metal that will react with dilute hydrochloric acid to give out hydrogen gas is Pb (lead). The reaction between lead and hydrochloric acid can be represented by the following equation:

Pb + 2HCl → PbCl2 + H2

**Reasoning:**
To determine which metal will react with hydrochloric acid, we need to consider the reactivity series of metals. The reactivity series is a list of metals in order of their reactivity, with the most reactive metal at the top and the least reactive metal at the bottom.

The reactivity series of metals is as follows:
Potassium (K) > Sodium (Na) > Calcium (Ca) > Magnesium (Mg) > Aluminum (Al) > Zinc (Zn) > Iron (Fe) > Lead (Pb) > Hydrogen (H) > Copper (Cu) > Silver (Ag) > Gold (Au)

According to the reactivity series, metals higher in the series are more reactive than metals lower in the series. This means that metals higher in the series can displace metals lower in the series from their compounds.

In the given options, lead (Pb) is below hydrogen (H) in the reactivity series. This means that lead can displace hydrogen from hydrochloric acid to form lead chloride (PbCl2) and release hydrogen gas (H2).

Therefore, the correct answer is option B - Pb.