Answer:
d. reduce her speed to the minimum at which she can be kept on her course if necessary.
Step-by-step explanation:
BOTH INTERNATIONAL & INLAND You hear the fog signal of another vessel forward of your beam. Risk of collision may exist. You MUST reduce her speed to the minimum at which she can be kept on her course if necessary.
Any vessel in situation of low or no visibility and hears the fog signal forward her beam is required to reduce her speed to the minimum at which she can be kept on her course or easily maneuvered. She shall if necessary take all her way off and in any event and navigate with extreme caution until danger of collision is over.