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: The seven unique crystal types are defined by faces parts of themselves (parts that intersect at various angles).

Answer: The seven unique crystal types are defined by what parts of themselves (parts that intersect at various angles)?


Question: Cell -> tissue -> organ -> organ system sequence represents the correct levels of organization for multicellular organisms.

Answer: Which sequence represents the correct levels of organization for multicellular organisms?


Question: Pyrogens bacteria are destroyed by leukocytes, what are released into the blood.

Answer:
When bacteria are destroyed by leukocytes, what are released into the blood?