What action must a vessel take if it is being overtaken?

Answer: A — Maintain its course and speed.

When a vessel is being overtaken, the appropriate action is to maintain its course and speed. This is in line with the rules that govern the conduct of vessels at sea, particularly the International Regulations for Preventing Collisions at Sea (COLREGs). The overtaking vessel is responsible for ensuring safe passage and must navigate around the other vessel without causing a collision. Maintaining course and speed provides predictability for the overtaking vessel, allowing it to assess the situation and safely maneuver around. If the overtaken vessel were to alter course or speed unexpectedly, it could create confusion and increase the risk of a collision. Therefore, the overtaken vessel plays a passive role by continuing as it is while the overtaking vessel makes the necessary adjustments to overtake safely. The other choices present actions that could potentially complicate the maneuvering situation. Changing course to the right or altering speed could confuse the overtaking vessel and increase the risk of collision. Signaling for the overtaking vessel to proceed may imply an active engagement that could disrupt the overtaking vessel's navigation strategy.