both international and inland while underway in the fog you hear the fog signal of another vessel ahead. if risk of collision exisits which action is requiered by the rules?

Slow to minimum at which the vessel can be kept on course

Explanation:

solution

according to rule 33 of Equipment for Sound Signals

when we hear signal of gong or bell or whistle

so when we hear sound so we should reduce our vehicle speed at very minimum speed to avoid the collision till we get safe exit vessel safely

so here correct answer is Slow to minimum at which the vessel can be kept on course