When directed to keep out of the way of another vessel, what should every vessel avoid?

Answer: B — Crossing ahead of the other vessel

When directed to keep out of the way of another vessel, the correct approach is to avoid crossing ahead of that vessel. This is because crossing ahead can put your vessel in a position where you might be in the path of the other vessel, leading to a higher risk of collision. In maritime navigation, the concept of "stand-on" and "give way" vessels is crucial. The give-way vessel must take action to avoid a collision and the most effective way to do this is to maintain a safe distance from the stand-on vessel's path. Therefore, instead of crossing ahead, which could potentially place your vessel in danger, it is safer to maneuver in a way that ensures you remain well clear of the other vessel’s trajectory. The other options, such as crossing behind, reducing speed, or turning portside, could still be viable strategies depending on the specific scenarios and vessel types involved. However, crossing ahead poses the greatest risk, as it could lead to a collision if both vessels continue on their respective courses.