This system has three primary functions, first it returns excess interstitial fluid to the blood second is for the absorption of fats and fat-soluble vitamins from the digestive system and the subsequent transport of these substances to the venous circulation and the third and probably most well-known function of this system is defense against invading microorganisms and disease A. Cardiovascular System B. Lymphatic System C. Digestive System D. Nervous System

The correct answer is **B. Lymphatic System**.<br /><br />Here's why:<br /><br />* **Returning excess interstitial fluid to the blood:** The lymphatic system collects fluid that leaks from blood capillaries and returns it to the bloodstream, preventing swelling and maintaining fluid balance.<br />* **Absorption of fats and fat-soluble vitamins:** Specialized lymphatic vessels called lacteals absorb fats and fat-soluble vitamins in the small intestine and transport them to the venous system.<br />* **Defense against invading microorganisms:** The lymphatic system contains lymph nodes and other lymphoid tissues that house immune cells (like lymphocytes) which fight off infections and diseases.<br /><br />The other options are incorrect:<br /><br />* **Cardiovascular System:** While involved in transporting fluids, it doesn't specifically collect interstitial fluid or absorb fats from the digestive system in the way the lymphatic system does.<br />* **Digestive System:** Focuses on breaking down food and absorbing nutrients, but the lymphatic system plays a key role in absorbing fats specifically.<br />* **Nervous System:** Primarily controls and coordinates bodily functions through electrical signals, not directly involved in fluid balance, fat absorption, or immune defense in the same way as the lymphatic system.<br />