Fact 1: Oxygen is just one substance transported by the blood. Fact 2: Breathing and circulation allow oxygen to be transported to the body's cells. Given the two facts above, what process provides one substance transported by the blood?

Options are: 1. breathing; 2. heat produced; 3. drink; 4. complex; 5. osmosis; 6. sweating; 7. cell division; 8. condensation;
Answer:
1.