The correct answer is B) Chafing gear. Chafing gear is used to prevent wear on towlines that bear on hard surfaces. It is a protective covering, such as a leather or synthetic sleeve, that is placed around the towline to prevent it from rubbing directly against the hard surface and becoming damaged. This helps maintain the integrity and strength of the towline, which is critical for safe towing operations. The other options are not the correct answer. Grease (A) would not provide adequate protection against abrasion, chocks (C) are used to secure equipment rather than protect towlines, and boots (D) are typically used to protect the ends of the towline, not the section that bears on hard surfaces.