Answer:
The correct answer is - keeping foreign particles out of the brain
Explanation:
The blood-brain barrier or BBB is the barrier of endothelial cells that is highly selective and semipermeable in nature that allows selective molecules like certain lipids, gas, and water and prevent other solutes and pathogens, toxins, and infectious agents from circulating blood between capillaries and brain. However, including specific gases and nutrients can cross this barrier.
Thus, the correct answer is - keeping foreign particles out of the brain
