The answer is A because the males sperm determines the sex of a baby.The determines sperm is carrying an X or Y chromosome.
 
        
             
        
        
        
Option C would be correct. The organ system can plays many parts at one time. Also, it is the only system listed.
Hope this helps!
        
                    
             
        
        
        
The answer is D. Extracellular,
the main ions involve in osmoregulation in a cell are sodium and chloride. Intra-and extracellular distribution of K+ is
influenced, for example, by Na+/K+-ATPase
function, pH, Cellular catabolism and anabolism, Insulin and glucose. Parathormone
and calcitriol are important in the homeostatic regulation of phosphates.