Step 1: Role of an Entrainer.
An entrainer modifies component volatilities in a distillation mixture to facilitate separation. For acetic acid and water, furfural is a common entrainer due to its formation of a heterogeneous azeotrope with water, enhancing separation efficiency.
Step 2: Option Evaluation.
- (A) Furfural is utilized as an entrainer for this separation. - (B) Benzol and (C) Butyl acetate are not standard entrainers for acetic acid-water mixtures. - (D) Hexane has different applications and is not employed as an entrainer in acetic acid-water separation.
Final Answer: \[\boxed{\text{A) Furfural}}\]