Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: The primary functions of the digestive system are to break down food, absorb nutrients and excrete wastes. Once food is absorbed, what system is responsible for carrying the nutrients to the body cells?
circulatory system
Circulatory system.