Given a scientific passage and an answer, generate a question for the given answer.
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Question: Passage: Cells are the tiny building blocks of living things. They couldn't be discovered until the microscope was invented. The discovery of cells led to the cell theory. This is one of the most important theories in life science. Answer: cells

Answer: What are all living things made of?

Question: Passage: Segmented worms include the common earthworm and leeches. Answer: segmented

Answer: The common earthworm and leeches are examples of what type of worm?

Question: Passage: One way mucous membranes protect the body is by producing mucus. Mucus is a sticky, moist secretion that covers mucous membranes. The mucus traps pathogens and particles so they can't enter the body. Answer: mucus

Answer:
A sticky, moist secretion that covers mucous membranes is called what?