Among the following metals, which does not produce `H_(2)` gas on reaction with dilute acids?
1. Zn 2. Al 3. Hg 4. Cu

Options

A. Zn and Al
B. Zn and Hg
C. Hg and Cu
D. Hg and Al

Explanation

To determine which metal does not produce hydrogen gas when reacting with dilute acids, we can analyze each of the given metals: Zinc (Zn), Aluminium (Al), Mercury (Hg), and Copper (Cu).

### Step-by-Step Solution:

1. **Understanding the Reaction of Metals with Dilute Acids:**
- When metals react with dilute acids, they typically displace hydrogen ions (H⁺) from the acid, leading to the evolution of hydrogen gas (H₂).

2. **Analyzing Each Metal:**
- **Zinc (Zn):**
- Zinc reacts with dilute acids (like HCl) to produce zinc chloride and hydrogen gas.
- Reaction:
\[ \text{Zn} + 2\text{HCl} \rightarrow \text{ZnCl}_2 + \text{H}_2 \uparrow \]
- Conclusion: Zinc produces hydrogen gas.

- **Aluminium (Al):**
- Aluminium also reacts with dilute acids to produce aluminium chloride and hydrogen gas.
- Reaction:
\[ 2\text{Al} + 6\text{HCl} \rightarrow 2\text{AlCl}_3 + 3\text{H}_2 \uparrow \]
- Conclusion: Aluminium produces hydrogen gas.

- **Mercury (Hg):**
- Mercury is less reactive than hydrogen. It does not react with dilute acids to produce hydrogen gas.
- Conclusion: Mercury does not produce hydrogen gas.

- **Copper (Cu):**
- Copper is also less reactive than hydrogen. It does not react with dilute acids to produce hydrogen gas.
- Conclusion: Copper does not produce hydrogen gas.

3. **Final Analysis:**
- From the analysis, we find that both mercury and copper do not produce hydrogen gas when reacting with dilute acids. However, since the question asks for the metal that does not produce hydrogen gas, we can select either of them. The most commonly accepted answer in this context is mercury.

### Answer:
The metal that does not produce hydrogen gas on reaction with dilute acids is **Mercury (Hg)**.