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: A decline in blood flow to kidneys organs stimulates release of the enzyme renin, in turn stimulating the reabsorption of sodium and water.

Answer: A decline in blood flow to what organs stimulates release of the enzyme renin, in turn stimulating the reabsorption of sodium and water?


Question: A mushroom is the fruiting body that occurs after two hyphae mate and form a mycelium with sporangia.

Answer: What is the fruiting body that occurs after two hyphae mate and form a mycelium with sporangia?


Question: In an electromagnetic wave, the crests and troughs represent oscillating fields.

Answer:
In an electromagnetic wave, what do the crests and troughs represent?