The true statement about benzene is

Options

A. Because of unsaturation benzene easily undergoes addition reactions
B. There are two types `C-C` bonds in benzene molecule
C. There is a cyclilc delocalisationof pi - electrons in benzene
D. Mono substitutionof benzene gives three isomeric products

Explanation

To determine the true statement about benzene, we will analyze the given statements one by one based on the properties and structure of benzene.

### Step-by-Step Solution:

1. **Understanding the Structure of Benzene:**
- Benzene (C₆H₆) is a cyclic compound with a hexagonal ring structure. Each carbon atom in benzene is sp² hybridized, which means that each carbon forms three sigma bonds and has one unhybridized p-orbital that contributes to the delocalized π-electron cloud above and below the plane of the ring.

2. **Analyzing the First Statement:**
- The first statement claims that benzene easily undergoes addition reactions due to unsaturation.
- **Evaluation:** Benzene is stable due to resonance and aromaticity. It does not easily undergo addition reactions; instead, it prefers substitution reactions to maintain its aromatic character. Therefore, this statement is **false**.

3. **Analyzing the Second Statement:**
- The second statement suggests that there are two types of C-C bonds in benzene.
- **Evaluation:** In benzene, all C-C bond lengths are equal due to resonance. There is no distinction between single and double bonds; thus, there is only one type of C-C bond. This statement is **false**.

4. **Analyzing the Third Statement:**
- The third statement states that there is a cyclic delocalization of π-electrons.
- **Evaluation:** This is true. The π-electrons in benzene are delocalized over the entire ring structure, contributing to its stability and aromaticity. This statement is **true**.

5. **Analyzing the Fourth Statement:**
- The fourth statement claims that monosubstitution of benzene gives three isomeric products.
- **Evaluation:** When benzene undergoes monosubstitution, it typically yields only one type of product due to the equivalence of hydrogen atoms on the benzene ring. Therefore, this statement is **false**.

### Conclusion:
The true statement about benzene is: **There is a cyclic delocalization of π-electrons.**

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