Consider the following reactions :
`2XS+3O_(2)overset(Delta)to 2XO+2SO_(2)`
`2XO+XS overset(Delta)to 3' X'+SO_(2)`
Then 'X' can not be :

Options

A. Hg
B. Pb
C. Zn
D. None

Explanation

To solve the question regarding the reactions and determine which element 'X' cannot be, we will analyze the given reactions step by step.

### Step-by-Step Solution:

1. **Identify the Reactions**:
We have two reactions:
- Reaction 1: \( 2XS + 3O_2 \overset{\Delta}{\rightarrow} 2XO + 2SO_2 \)
- Reaction 2: \( 2XO + XS \overset{\Delta}{\rightarrow} 3X' + SO_2 \)

2. **Understand the Concept of Self-Reduction**:
- In the first reaction, 'XS' reacts with oxygen to form 'XO' and sulfur dioxide.
- In the second reaction, 'XO' reacts with 'XS' to produce a new element 'X'' and more sulfur dioxide.
- The term "self-reduction" indicates that the same element is both oxidized and reduced in the reactions.

3. **Identify Elements that Undergo Self-Reduction**:
- Elements known to undergo self-reduction include silver (Ag), mercury (Hg), and lead (Pb). These elements can participate in reactions where they can reduce themselves.

4. **Analyze the Options**:
- We need to determine which of the provided options cannot be 'X'.
- Based on the self-reduction concept, we can conclude that:
- Silver (Ag), Mercury (Hg), and Lead (Pb) can be 'X'.
- Zinc (Zn), however, does not undergo self-reduction; it typically requires a reducing agent for reduction.

5. **Conclusion**:
- Since zinc does not undergo self-reduction, it cannot be 'X'. Therefore, the answer to the question is that 'X' cannot be zinc.

### Final Answer:
**'X' cannot be: Zinc (Zn)**