Answer:
The answer is B
Explanation:
I hope you have/had an amazing day today and may God bless you<3
 
        
                    
             
        
        
        
Answer:
The barrier functions to regulate the chemical composition of the extracellular fluid surrounding the brain cells.
Explanation:
Blood-brain barrier
It is a very selective semipermeable membrane , hence allow some specific substance to pass via it . This barrier separates the  extracellular fluid in the central nervous system  and the circulating blood from the brain .
<u>The barrier is composed of the endothelial cells .</u>
Passive diffusion is shown in this system , and allows molecules like the water , glucose , amino acid to pass .
It regulates the chemical composition of the fluid of brain cell .
 
        
             
        
        
        
A. the runner's muscles have accumulated lactic acid.. I think.  99% sure
        
                    
             
        
        
        
A light that shines in all living things