What must be done first before placing the tape for measuring abdomen circumference?

Before measuring abdominal circumference, ensuring that the shoulders are down and the arms are relaxed is essential. This position promotes a natural stance, which helps to avoid any unnecessary tension or pulling in the upper body that could skew the measurement. When the Marine stands in a relaxed posture, it allows for a more accurate reading as the abdomen is not inadvertently pulled in or out, providing a true circumference measurement.

The other options may not directly contribute to the accuracy of the measurement. For example, standing on one leg could create instability and affect the measurement. Shoes are typically removed for body measurements to ensure consistency and accuracy. Lastly, looking down doesn’t influence the abdomen's positioning in a way that contributes to an accurate measurement. Therefore, focusing on relaxation and proper posture is critical for achieving reliable results.