The primary functions of the circulatory system include transporting oxygen and nutrients to cells, removing waste products, and regulating body temperature. While it does play a role in hormone transport, it does not directly produce hormones. Therefore, the option “All of the following” would not be accurate since breaking down nutrients is primarily the role of the digestive system rather than the circulatory system.
So, the best answer reflecting the primary functions of the circulatory system is "Regulating body temperature."