Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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Question: Mucous does the esophagus produce for lubrication.

Answer: What does the esophagus produce for lubrication?


Question: Plasma matter makes up most of the universe.

Answer: What type of matter makes up most of the universe?


Question: Prokaryotic cells' organelles because not membrane-bound.

Answer:
What are unique about prokaryotic cells' organelles?