When towing astern, you notice that another vessel is about to pass between the towing vessel and the tow. You should immediately __________.

Correct Answer: Option A — slow down and pay out the main tow hawser

If a vessel attempts to pass between the tug and tow, the master must immediately slow down and pay out the hawser. This action increases the depth of the catenary, allowing the passing vessel to safely cross over the towline without fouling the gear or causing a collision.