Which of the following is an example of a combined command?

A combined command typically consists of two separate actions or commands that are intended to be executed simultaneously. In this scenario, "At ease" is identified as the correct answer because it allows service members to assume a more relaxed position while maintaining an awareness of their surroundings, thus combining the action of relaxing with the requirement to remain alert.

In contrast, commands like "March forward," "Attention," and "Turn left" are examples of single, direct commands that indicate a specific action to be taken by the troops. Each of these requires a distinct, immediate response without the combination of actions inherent in a combined command.