Which of the following is a position where a Marine can stand relaxed but still attentive?

The position referred to as "At Ease" is designed for a Marine to stand relaxed while remaining attentive. When in this position, the Marine stands with feet shoulder-width apart, hands clasped behind the back, and the head and eyes turned forward. This allows for a more comfortable posture that is less formal than the position of attention, but still maintains a level of readiness and awareness.

Being "At Ease" strikes a balance between relaxation and alertness, making it suitable for situations where the Marine is not actively involved but is still required to maintain a presence.

In contrast, the other choices represent different levels of formality or relaxation. "Parade Rest" is a more formal position that requires a specific stance and is typically used in ceremonies. "Stand Easy" allows for some movement but still requires alertness, while "Rest" is a completely relaxed position typically used when the Marine is not required to be attentive. Each of these positions serves different purposes, but "At Ease" is specifically tailored to maintain an attentive posture while allowing for relaxation.