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: The female reproductive system consists of structures that produce eggs, secrete female sex hormones, and ultimately enable birth of a fetus.

Answer: What system consists of structures that produce eggs, secrete female sex hormones, and ultimately enable birth of a fetus?


Question: The main advantage of urea is its very low toxicity.

Answer: The main advantage of urea is its very low what?


Question: Ocean acidification occurs when excess carbon dioxide in the atmosphere causes the oceans to become acidic.

Answer:
What occurs when excess carbon dioxide in the atmosphere causes the oceans to become acidic?