To determine the correct sequence, we infer the intended transformation from the reagent patterns.

The only option that gives a very standard aromatic conversion is:

$\text{benzene} \xrightarrow{Br_2/Fe} \text{bromobenzene} \xrightarrow{Fe/H^+} \text{aniline-type reduction step not possible directly from bromobenzene}$

So we must analyze more carefully.

A much more common multistep sequence in this chapter is:

$\text{toluene} \rightarrow p\text{-/o-bromo derivative} \rightarrow \text{amino derivative} \rightarrow \text{diazonium salt} \rightarrow \text{chloro derivative} \rightarrow \text{benzoic acid}$

Let us check which option matches a logical synthetic route.

1. Identify the role of each reagent

1. $\mathrm{Br_2/Fe}$ : bromination of an aromatic ring.
2. $\mathrm{Fe/H^+}$ : reduction of a nitro group: $\mathrm{-NO_2 \to -NH_2}$
3. $\mathrm{HONO}$ : diazotization of a primary aromatic amine: $\mathrm{ArNH_2 \to ArN_2^+}$
4. $\mathrm{CuCl}$ : Sandmeyer reaction: $\mathrm{ArN_2^+ \to ArCl}$
5. $\mathrm{KMnO_4}$ : oxidation of benzylic side chain to carboxylic acid: $\mathrm{-CH_3 \to -COOH}$

2. Test the options

Option A

$(i)\ \mathrm{KMnO_4},\ (ii)\ \mathrm{Br_2/Fe},\ (iii)\ \mathrm{Fe/H^+},\ (iv)\ \mathrm{Cl_2}$

This is not logical because $\mathrm{Fe/H^+}$ requires a reducible group such as $\mathrm{-NO_2}$, but no nitration step is present.

So, A is incorrect.

Option B

$(i)\ \mathrm{Fe/H^+},\ (ii)\ \mathrm{HONO},\ (iii)\ \mathrm{CuCl},\ (iv)\ \mathrm{KMnO_4},\ (v)\ \mathrm{Br_2}$

Again, the first step $\mathrm{Fe/H^+}$ requires a nitro compound already present. Also bromination at the end is inconsistent with the usual target sequence.

So, B is incorrect.

Option C

$(i)\ \mathrm{Br_2/Fe},\ (ii)\ \mathrm{Fe/H^+},\ (iii)\ \mathrm{HONO},\ (iv)\ \mathrm{CuCl},\ (v)\ \mathrm{KMnO_4}$

This option contains a coherent standard sequence if the substrate already contains a reducible nitro group and a side chain. The steps are:

1. Bromination of aromatic ring using $\mathrm{Br_2/Fe}$.
2. Reduction of $\mathrm{-NO_2}$ to $\mathrm{-NH_2}$ using $\mathrm{Fe/H^+}$.
3. Diazotization using $\mathrm{HONO}$.
4. Replacement by Cl using $\mathrm{CuCl}$.
5. Oxidation of benzylic side chain to $\mathrm{-COOH}$ using $\mathrm{KMnO_4}$.

This is a very standard and chemically valid progression.

So, C is correct.

Option D

$(i)\ \mathrm{Br_2/Fe},\ (ii)\ \mathrm{Fe/H^+},\ (iii)\ \mathrm{KMnO_4},\ (iv)\ \mathrm{Cl_2}$

Again, there is no diazotization/Sandmeyer sequence, so introducing chlorine in a selective aromatic substitution sense is not justified.

So, D is incorrect.

3. Final Answer

The correct sequence of reagents is:

$\boxed{\text{C}}$

4. Comparison with stored answer

Stored correct answer = C.

My derived answer = C.

So, they agree.