In which of the following reactions, aromatic character is retained?

Options

A. `C_(6)H_(6)overset(H_(2)//Ni)rarrX`
B. `C_(6)H_(6)overset(O_(3))underset(Zn//H_(2)O)rarrY`
C. `C_(6)H_(6)overset(CH_(3)COCl)underset(AlCl_(3))rarrQ`
D. `C_(6)H_(6)overset(Cl_(2))underset("light")rarr R`

Explanation

To determine which of the reactions retains aromatic character, we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Option A: Benzene with H2 and Nickel**
- When benzene (C6H6) reacts with hydrogen (H2) in the presence of a nickel catalyst, it undergoes hydrogenation. This reaction converts benzene into cyclohexane (C6H12), which is a saturated compound and does not retain the aromatic character.
- **Conclusion:** Aromatic character is lost. **(Cancel this option)**

2. **Option B: Benzene with Ozone (O3) and Water**
- In this reaction, benzene reacts with ozone followed by hydrolysis (addition of water). The ozonolysis of benzene leads to the formation of three molecules of carbonyl compounds (like ketones or aldehydes), which do not retain the aromatic character of the original benzene.
- **Conclusion:** Aromatic character is lost. **(Cancel this option)**

3. **Option C: Benzene with CH3COCl in presence of AlCl3**
- This reaction is a Friedel-Crafts acylation. Benzene reacts with acetyl chloride (CH3COCl) in the presence of aluminum chloride (AlCl3) to form acetophenone (C6H5COCH3). The aromatic ring remains intact and retains its aromatic character throughout the reaction.
- **Conclusion:** Aromatic character is retained. **(This option is valid)**

4. **Option D: Benzene with Cl2 in presence of sunlight**
- In this reaction, benzene reacts with chlorine (Cl2) in the presence of sunlight, leading to the substitution of hydrogen atoms with chlorine atoms. This is a free radical substitution reaction. However, the aromatic character of benzene is retained as the structure of the benzene ring remains intact.
- **Conclusion:** Aromatic character is retained. **(This option is valid)**

### Final Answer:
- The reactions that retain aromatic character are **Option C** (Benzene with CH3COCl in presence of AlCl3) and **Option D** (Benzene with Cl2 in presence of sunlight).