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: Air quality is a measure of pollutants in the air.

Answer: Air quality is a measure of what in the air?


Question: Amount of salt are aquatic biomes often classified.

Answer: How are aquatic biomes often classified?


Question: The average global temperature has been rising since the end of pleistocene era.

Answer:
The average global temperature has been rising since the end of what era?