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

Q: Passage: When a fluorine atom gains an electron, it becomes a negative fluoride ion. Answer: fluoride ion

A: When a fluorine atom gains an electron, it becomes a negative what?
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Q: Passage: tobacco smoke causes fatal lung disease in nonsmokers. Answer: tobacco smoke

A: What still causes fatal lung disease in nonsmokers?
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Q: Passage: Vacuoles are membrane-bound organelles that can have secretory, excretory, and storage functions. Many organisms will use vacuoles as storage areas and some plant cells have very large vacuoles. Vesicles are much smaller than vacuoles and function in transporting materials both within and to the outside of the cell. Answer: vacuoles

A:
What are membrane-bound organelles that can have secretory, excretory, and storage functions?
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