科研之友
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摘要
<正>Jellyfish are soft bodied.They swim in the sea freely.Jellyfish have an umbrella-shaped(伞状的)bell.They are like mushrooms in the sea.Some jellyfish are small.Some jellyfish are very big.They are mostly made up of water.Jellyfish have roamed the seas for at least 500 million years.They are the oldest multi-organ(多器官)animal.
