Given a scientific passage and an answer, generate a question for the given answer.

Input: Consider Input: Passage: The bodies of organisms can make a sedimentary rock. Plant bodies are lithified to become coal. When shells are cemented together they make a type of limestone. So limestone can be considered chemical or organic. Answer: coal

Output: What is formed when plant bodies are lithified?


Input: Consider Input: Passage: Hair, hair follicle, and oil glands. The oil, called sebum, helps to prevent water loss from the skin. The sebaceous gland secretes sebum, which waterproofs the skin and hair. Answer: sebum

Output: What does the sebaceous gland secrete which waterproofs the skin and hair?


Input: Consider Input: Passage: Some animal-like protists use their "tails" to eat. These protists are called filter-feeders . They acquire nutrients by constantly whipping their tails, called flagellum , back and forth. The whipping of the flagellum creates a current that brings food into the protist. Answer: filter-feeders


Output: Protists which use their tails to eat are called what?


