The correct answer is D) A vessel is on your starboard quarter, range decreasing, bearing is constant. This situation definitely indicates a risk of collision because the bearing of the other vessel is constant, which means it is on a steady course towards your vessel. Additionally, the range is decreasing, which means the distance between the two vessels is closing. According to the International Regulations for Preventing Collisions at Sea (COLREGS), when two vessels are on a collision course, the vessel that has the other on its starboard side is the stand-on vessel and must maintain its course and speed. The other options are incorrect because they do not necessarily indicate a risk of collision. In option A, the vessel's bearing is changing slightly, suggesting it is not on a steady collision course. In option B, the vessel's bearing is changing rapidly, indicating it is not on a steady collision course. In option C, the vessel's range is increasing, which means the distance between the two vessels is growing, not closing.