The correct answer is B) trim the tow by the stern. Trimming the towed vessel by the stern helps to control the side-to-side veering of the tow. By shifting more weight to the stern, the tow's hydrodynamics are improved, allowing it to track more steadily behind the towing vessel. This is in accordance with standard seamanship practices for controlling the motion of a tow astern. The other options are incorrect because: A) listing the tow to windward would not directly address the side-to-side veering, C) trimming by the bow would worsen the tow's tendency to yaw, and D) adjusting the towing bridle length may help in some cases but is not the best primary means of controlling the tow's motion.