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

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: A covalent network solid is a compound in which all of the atoms are connected to one another by covalent bonds.

A: What is a compound in which all of the atoms are connected to one another by covalent bonds?
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Q: Hydrogen sulfide is a noxious and toxic gas produced from decaying organic matter that contains sulfur.

A:
Hydrogen sulfide is a noxious and toxic gas produced from decaying organic matter that contains what?
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