The correct answer is C) have a guard over the gearing. The reasoning behind this is that mechanical gearing on deck machinery, such as a windlass or towing engine, should be guarded to prevent accidental contact and potential injury to crew members. Exposing the gearing would create a safety hazard, and it is a regulatory requirement to have guards in place to cover these moving parts. The other options are incorrect because: A) painting the gearing a contrasting color does not provide the necessary physical barrier, B) restricting crew proximity is not a substitute for guarding the machinery, and D) allowing the gearing to be openly exposed goes against safety regulations and best practices for marine machinery.