Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

Q: All enzymes have an optimal temperature and ph.

A: All enzymes have an optimal temperature and what?
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Q: Salt-water biomes in the ocean are called marine biomes.

A: Salt-water biomes in the ocean are called what?
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Q: The common cold and flu are examples of human diseases caused by viruses.

A:
The common cold and flu are examples of human diseases caused by what tiny particles?
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