What could be a sign of potential intoxication observed in a passenger?

Losing train of thought can be a significant indicator of potential intoxication in a passenger. This behavior might manifest as difficulty in maintaining a coherent conversation, struggling to follow discussions, or frequently forgetting what was just said. When a person is intoxicated, their cognitive functions can be impaired, leading to challenges in attention and memory. Observing a passenger who seems disoriented or unable to stay focused may warrant further attention as it can suggest they are not in a stable state.

The other options do not typically suggest signs of intoxication. Active engagement in conversation might be indicative of a sociable individual, while using headphones continuously could simply reflect someone's preference for isolation or enjoyment of music or podcasts. Reading a book is often a sign of a passenger seeking a quiet activity and is not generally associated with intoxication. Thus, losing train of thought is a more direct indicator that something may be off, especially if it deviates from the passenger's usual behavior.