Small, visible mound-like protuberances on the bottom of cumulonimbus clouds, that are potential breeding grounds for waterspouts and tornadoes, are called __________.

Correct Answer: Option C — mamma

Mammatus clouds (mamma) feature pouch-like protuberances hanging from the base of cumulonimbus clouds, frequently associated with severe turbulence, tornadoes, and waterspout formation.