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Many types of bacteria are helpful. For example, some are able to take nitrogen from the air. They then put it into the soil. This makes the soil better for growing plants. Some bacteria are helpful in making cheese. Other bacteria are helpful in making vinegar. What is the main idea of this text passage? A. Bacteria puts nitrogen from the air into the soil. B. Bacteria helps make food. C. Some types of bacteria helps humans.
What is C. "Some types of bacteria helps humans."