Under what condition can the stand-on vessel take action to avoid collision?

Answer: B — When the give-way vessel does not take early and substantial action

The stand-on vessel is typically required to maintain its course and speed to promote predictability in navigation when it has the right of way. However, there are specific circumstances where this vessel may take action to avoid a collision. The key situation is when the give-way vessel, which is responsible for yielding, fails to take early and substantial action to avoid the impending collision. If the stand-on vessel perceives that the give-way vessel is not making adequate maneuvers to mitigate the risk of a collision, it may then take appropriate measures to avoid the situation. This exception is crucial for maritime safety because inaction by the give-way vessel could lead to a dangerous scenario, necessitating a response from the stand-on vessel to ensure the safety of both vessels involved. This allows the stand-on vessel to act proactively in situations where its safety, or the safety of others, is at risk, even while it would normally be expected to hold its course.