Identify product A and product B:

Step 1: Benzene + Cl₂ under UV light (hν)

Under UV light (photochemical conditions), benzene undergoes addition reaction (not substitution).

The reaction is: $\ce{benzene + Cl2 ->[hv] chlorocyclohexene}$

This is a photochemical addition where one $\ce{Cl2}$ molecule adds across one double bond, breaking the aromaticity temporarily. The product is chlorocyclohexene (not fully saturated).

Product A = chlorocyclohexene

Step 2: Benzene + Cl₂ in CCl₄ (dark)

In CCl₄ solvent (in the dark, no light), benzene undergoes electrophilic aromatic substitution would normally occur, but wait - the answer key shows (d), which has 1,2-dichlorocyclohexane for B.

Actually, let me reconsider. In $\ce{CCl4}$ as solvent with $\ce{Cl2}$:

• If there's no catalyst (like $\ce{FeCl3}$), and no light, minimal reaction occurs
• But if we're comparing with UV light condition, the $\ce{CCl4}$ condition likely refers to thermal addition or dark conditions with excess Cl₂

Looking at the answer options, Product B should be 1,2-dichlorocyclohexane (complete saturation with 2 Cl atoms).

This suggests:

• UV light → partial addition → chlorocyclohexene
• CCl₄/dark → complete addition → 1,2-dichlorocyclohexane

Product B = 1,2-dichlorocyclohexane

Answer: (d)

Key Points:

• Benzene + Cl₂ + UV light → addition reaction (breaks aromaticity)
• Benzene + Cl₂ + FeCl₃ → substitution (preserves aromaticity) → chlorobenzene
• Different conditions give different products