C. "like startled rattlesnakes, the long/naked arms uncoil"
Explanation:
Moving their arms around while clicking the castanets would make them look and sound like rattlesnake, so "like startled rattlesnakes, the long/naked arms uncoil" is the answer. Castanets are used to create a rhythm or to create drama in many Spanish dances.
There's no real or better indication of sound in the other quotes provided as possible answers.
