Final answer:
The correct answer is regulation of calcium ion concentration in the blood. This is not a basic function of the lymphatic system, which is primarily concerned with immune functions, regulation of interstitial fluid volume, and absorption of dietary fats.
Step-by-step explanation:
The lymphatic system performs several critical functions, including immune function, the regulation of interstitial fluid volume, and the absorption of dietary fats. However, it does not play a direct role in the regulation of calcium ion concentration in the blood. Calcium concentration regulation is primarily the function of the endocrine system, particularly the parathyroid hormone and calcitonin that act on the bones, kidneys, and intestine.
The lymphatic system's roles include host defense, such as producing and maturing lymphocytes that are integral to the immune response. It absorbs interstitial fluid and returns it to the bloodstream, thus maintaining fluid balance in the body. The system also absorbs fatty acids from the digestion of lipids via lacteals in the intestines, contributing to nutrient absorption. These absorbed fats and lipids are then transported through the network of lymphatic vessels to the bloodstream.