Identify the likely transformation

From the reagent sets, the sequence clearly suggests:

• Protection of aniline using acetic anhydride: $\mathrm{Ac_2O}$
• Bromination of the protected aniline derivative
• Hydrolysis/deprotection with hot water / acidic medium
• Basic workup with $\mathrm{NaOH}$

This is the standard method used when converting aniline to p-bromoaniline selectively.

Why protection is needed

Direct bromination of aniline gives uncontrolled polybromination because the $-\mathrm{NH_2}$ group is strongly activating.

So first aniline is acetylated: $\mathrm{C_6H_5NH_2 \xrightarrow{Ac_2O} C_6H_5NHCOCH_3}$ forming acetanilide.

Role of bromination step

Acetanilide is still ortho/para directing, but less activating than aniline, so bromination gives mainly p-bromoacetanilide.

Need of acid before acetylation

Among the options, the correct practical sequence for preparing the acylated intermediate and then carrying out bromination/deprotection includes use of $\mathrm{H_2SO_4}$ along with acetylation/hydrolysis conditions. The presence of acid facilitates the process leading to the protected derivative and subsequent hydrolysis.

Check options

Option A: $\mathrm{Ac_2O, Br_2, H_2O}(\Delta), NaOH$

• Looks close to protection $\to$ bromination $\to$ hydrolysis $\to$ neutralization.
• But the standard set given in such conversions generally includes acidic medium for acetylation/hydrolysis handling.

Option B: $\mathrm{H_2SO_4, Ac_2O, Br_2, H_2O}(\Delta), NaOH$

• Acidic condition first, then acetylation, then bromination, then hydrolysis on heating, and finally base.
• This matches the expected multi-step conversion best.

Option C: $\mathrm{Br_2/FeBr_3, H_2O}(\Delta), NaOH$

• No protection step.
• Direct bromination of aniline is not suitable; also $\mathrm{FeBr_3}$ is not used this way for aniline due to coordination/deactivation complications.
• Incorrect.

Option D: $\mathrm{Ac_2O, H_2SO_4, Br_2, NaOH}$

• Missing hydrolysis step with water/heating.
• Incorrect.

Conclusion

Therefore, the correct order of reagents is: $\boxed{\text{B}}$