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Given a scientific passage and an answer, generate a question for the given answer.

Passage: Plants can also reproduce sexually, but their reproductive organs are different from animals' gonads. Plants that have flowers have their reproductive parts in the flower. The sperm is contained in the pollen, while the egg is contained in the ovary, deep within the flower. The sperm can reach the egg two different ways:. Answer: the sperm
Output:
What reproductive part is stored in a plant's pollen?