You are approaching another vessel and are not sure whether danger of collision exists. You must assume __________.

The appropriate assumption when approaching another vessel and uncertain about the risk of collision is that there is a risk of collision. This aligns with the fundamental principles of navigation and the rules set forth in the International Regulations for Preventing Collisions at Sea (COLREGs). The rules emphasize the importance of maintaining a safe navigation posture and taking proactive measures to avoid collisions.

Assuming there is a risk of collision encourages mariners to be vigilant and prepared to take preventative actions, such as altering course or speed, to ensure safety. This mindset is crucial in busy waterways or situations where visibility is limited, as it helps to avoid potential accidents.

In contrast, assuming there is no risk of collision could lead to complacency and potentially dangerous situations. Similarly, expecting the other vessel to take action or claiming the right of way without assessing the circumstances could increase the likelihood of a collision, as it does not account for the unpredictability of other vessels' movements or decisions. Therefore, the most prudent approach is to assume a risk of collision exists until proven otherwise.