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

Q: Oxygen is transferred through capillaries.

A: Which blood vessels is oxygen transferred through?
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Q: Fungi is the major cause of disease in agricultural crops.

A: What is the major cause of disease in agricultural crops?
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Q: Condensation must occur for clouds to form.

A:
Which process must occur for clouds to form?
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