Clothing exposed to flames should not:

The option indicating that clothing exposed to flames should not increase injury or burn after the heat is removed is important because it emphasizes the necessity of choosing appropriate materials that minimize prolonged injury risks. Clothing that retains heat or continues to burn after the initial exposure can lead to severe injuries, as it may continue to damage the skin even after the fire has been extinguished.

Materials that are designed to self-extinguish or do not retain heat are critical in the context of fire safety. Fire-resistant clothing is specifically engineered to reduce the likelihood of burns; such clothing often stops burning as soon as the source of ignition is removed, preventing further injury.

The other options relate to specific characteristics of clothing but do not address the immediate concern of post-exposure injury. For instance, thick and heavy clothing can provide better protection initially, while natural fibers may ignite easily. Meanwhile, synthetic materials can melt and stick to the skin, increasing injury risks. However, the fundamental goal is to ensure that clothing does not exacerbate injuries once the immediate threat of flames has been mitigated.