Concept:The word "pachyderm" is formed from Greek roots meaning "thick" and "skin."Explanation:"Pachyderm" comes from Greek: pachys meaning "thick" and derma meaning "skin."It is used to describe a mammal that has very thick skin.Common examples are elephants, rhinoceroses, and hippopotamuses.Therefore, the correct meaning is "a thick-skinned mammal."Option A matches this definition exactly.Answer:Option A: A thick-skinned mammal