What type of clothing is specifically designed to shield the wearer from high thermal hazards?

The correct choice identifies the proximity suit as specifically designed to protect the wearer from high thermal hazards. Proximity suits are crafted to withstand intense heat and are typically used by fire responders and workers dealing with high-temperature environments. They provide excellent insulation while allowing for mobility and protection from radiant heat, which is crucial in environments where extreme temperatures are present.

In contrast, environmental suits are generally aimed at protecting the wearer from chemical hazards, not primarily thermal hazards. Safety boots, while important for overall personal protective equipment, focus mainly on foot protection and do not provide high thermal resistance. Wetsuits are designed to retain body heat in water, making them suitable for cold aquatic environments but not for protection against high thermal hazards present in fires or intense heat sources.