Cells to Systems Challenge

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Across
  1. 2. This system carries oxygen and nutrients throughout the body.
  2. 4. The system that breaks down food for energy.
  3. 6. The main organ of the nervous system.
Down
  1. 1. The smallest unit of life.
  2. 3. This system is responsible for breathing.
  3. 5. A group of organs working together.