Which of the following is NOT a treatment for motion sickness?

Not keeping the cabin closed is a valid approach to helping alleviate motion sickness, as it allows for fresh air circulation, which can help reduce the symptoms. When a cabin is closed, it may contribute to stuffiness and discomfort, potentially worsening feelings of nausea.

In contrast, avoiding caffeine can be beneficial, as it might increase jitteriness and exacerbate symptoms of motion sickness. Focusing on nearby objects is a common technique to help stabilize one’s vision in relation to the surrounding environment, potentially aiding in reducing the sensation of motion sickness. Opening fresh air vents can also provide a refreshing airflow that can alleviate symptoms. Thus, keeping the cabin closed does not align with effective treatments for motion sickness, making it the correct response in this context.