A suitable undergarment shall be worn under which of the following?

A wrestling singlet is designed to fit snugly on the body, providing support and minimizing the risk of injury during competition. Wearing an appropriate undergarment underneath the singlet is recommended for both comfort and hygiene reasons. The undergarment helps prevent any potential interactions between the body and the singlet material, such as chafing or irritation, which can arise from skin-on-skin contact.

In contrast, regular shorts, sweatpants, and t-shirts may not need specific undergarments since they do not have the same tight fit and aren't subject to the same friction and movement during wrestling activities. While athletes might choose to wear undergarments for comfort in these other clothing types, they are not required for the purpose of supporting or protecting the body in the way a singlet does.