In this task, you need to write a topic word from the given fact. The topic word must have at least one word overlap with the given fact. The topic word often involves adding a new word from a related concept. In your topic word, use at least one word from the given fact. Topic words with two or more words work best.

Q: Fact: Passive immunity lasts only as long as the antibodies survive in body fluids.

A: antibodies protein.
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Q: Fact: sinkholes are formed by precipitation.

A: precipitation are formed by.
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Q: Fact: Vertebrates are animals that have a backbone.

A:
backbone muscles move.
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