Wrestlers must wear which of the following to ensure compliance during matches?

Wrestlers must wear singlets during matches to ensure compliance with the sport's regulations and to facilitate fair competition. Singlets are designed specifically for wrestling, providing not only a snug fit that avoids entanglement but also allowing officials to see the wrestler's movements clearly, which is crucial for scoring. The design of singlets supports both functionality and safety by minimizing the risk of injury due to loose clothing or improper gear.

Other types of clothing, such as flip-flops, shorts, or regular t-shirts, do not meet the requirements of wrestling attire. Flip-flops are not suitable for competition due to safety concerns, while shorts and t-shirts do not offer the structure needed for performance in a wrestling context. Therefore, wearing a singlet is essential for both compliance with wrestling rules and to maintain a professional standard during matches.