What is the body fluid that transports substances throughout the body and is only found in lymphatic vessels?

Lymph is the correct answer because it is a clear fluid that is part of the lymphatic system, which plays a crucial role in immune function and the maintenance of fluid balance in the body. Lymph specifically circulates through lymphatic vessels, transporting immune cells, especially lymphocytes, as well as waste products and excess interstitial fluid collected from tissues.

In contrast, serum is a component of blood that remains after coagulation and contains various proteins, nutrients, hormones, and waste products, but it is not exclusive to lymphatic vessels. Plasma, also derived from blood, is the liquid portion that contains blood cells and proteins and circulates through the cardiovascular system, not the lymphatic system. Lastly, interstitial fluid is the fluid that exists in the spaces between cells in tissues and can be collected into lymph but is not itself found exclusively in lymphatic vessels. Thus, lymph is distinctive for its specific association with the lymphatic system.