The correct answer is C) a face mask or goggles. When sampling hazardous cargo on a tankship, the minimum required protective clothing includes a face mask or goggles to protect the eyes and face from potential exposure to hazardous materials. This is in accordance with the safety regulations and guidelines set forth by the US Coast Guard for handling hazardous cargo on vessels. The other options, while potentially useful in certain situations, are not the minimum required for this specific task. Boots and chemical-resistant gloves are also important, but a face mask or goggles are the critical piece of protective equipment needed to safely sample hazardous cargo.