Final answer:
After nutrients are absorbed by the circulatory system, they first pass through the liver, where they are processed before returning to the heart and circulating to the rest of the body.
Step-by-step explanation:
Once nutrients are absorbed into the circulatory system, the next major organ they pass through is the liver. The veins that collect nutrient-rich blood from the small intestine, where most nutrient absorption occurs, empty into the hepatic portal system. This system takes the blood to the liver, where the nutrients are processed or stored. Only after leaving the liver does the blood make its way back to the heart to be circulated to the rest of the body. Therefore, the correct answer to the question is b. liver.