1. Interpret the reagent sequences

We need to identify which sequence can bring about the required aromatic side-chain transformation.

The key reagent patterns are:

• $\mathrm{Br}_2/\mathrm{Fe}$ or $\mathrm{Cl}_2/\text{anhy. }\mathrm{AlCl}_3$ $\rightarrow$ electrophilic aromatic substitution on benzene ring.
• $\mathrm{Cl}_2, \Delta$ $\rightarrow$ free-radical side-chain chlorination at benzylic position.
• alc. KOH $\rightarrow$ generally elimination.
• aq. KOH $\rightarrow$ generally nucleophilic substitution / hydrolysis.

So, if the conversion involves:

• first introducing a halogen on the ring,
• then chlorinating the side chain,
• then eliminating HCl to form an alkene,

we need the sequence:

2. Check each option

Option A

• First two steps are both aromatic halogenations.
• No side-chain chlorination step like $\mathrm{Cl}_2,\Delta$ is present.
• Hence this sequence cannot generate a benzylic halide needed for elimination.

So, A is incorrect.

Option B

• Again, first two are ring halogenation steps.
• No benzylic radical chlorination.
• Final reagent is aq. KOH, which favors substitution, not elimination.

So, B is incorrect.

Option C

• $\mathrm{Br}_2/\mathrm{Fe}$: bromination of benzene ring.
• $\mathrm{Cl}_2,\Delta$: benzylic chlorination of side chain.
• alc. KOH: elimination of HCl from side-chain chloride to form the corresponding alkene.

This is the chemically consistent sequence.

So, C is correct.

Option D

• First step (ring bromination) is acceptable.
• Second step (side-chain chlorination) is also acceptable.
• But final step uses aq. KOH, which would tend to give substitution/hydrolysis rather than the required elimination.

So, D is incorrect.

3. Conclusion

The only suitable reagent set is:

4. Comparison with stored answer

Stored correct answer: C

My derived answer: C

Hence, they agree.