Calcium ion is responsible for Muscle Contractions.
        
             
        
        
        
The awnser is B my good sir
 
        
                    
             
        
        
        
I believe the answer is E) Input
        
             
        
        
        
Cell membrane is made up of Lipid Bilayer which are fluid in nature , means they move continuosly , due to this fluid nature they are selectively permeable to compounds.