The correct answer is C) Gob ropes. Gob ropes are used to prevent the tripping of a tug during towing operations. They are lines attached to the tow line that help keep the tow from riding up and over the stern of the tug, which can cause the tug to trip and capsize. This is a common safety measure employed by tug operators to maintain control and stability during towing. The other answer choices, while related to towing equipment, are not specifically used to prevent the tripping of a tug. Drogues are used to provide resistance and slow the towed vessel, bridles are used to connect the tow line to the towed vessel, and chafing boards protect the tow line from wear and abrasion, but they do not directly address the issue of tug tripping.