The correct answer is A) Stand-on. In an overtaking situation, the stand-on vessel (the vessel being overtaken) must maintain its course and speed. The overtaking vessel, which is showing an alternately flashing red-and-yellow light, is required to take early and substantial action to safely pass the stand-on vessel. As the stand-on vessel, you should continue on your course and speed, allowing the overtaking vessel to safely pass you. The other answer choices are incorrect because: B) Altering course to assist would be the responsibility of the overtaking vessel, not the stand-on vessel. C) Heaving to is not the appropriate action for the stand-on vessel in this situation. D) Giving way would be the incorrect action for the stand-on vessel.