Randy, a salon owner, is attending an annual cosmetology fair. This afternoon, he is circling around the numerous product booths in the main auditorium. He comes across the "speed lecture" area of the auditorium, where Alan, a researcher for a cosmetics company, holds a session to explain the basics of cosmetic chemistry. Not to be outperformed, Randy raises his hand to identify the other type of surfactant, _____, which are the agents that cause cleansers to foam and remove oil, dirt, makeup, and debris from the surface of the skin.