Answer:
Each time your heart beats, an electrical signal travels through the heart. An EKG can show if your heart is beating at a normal rate and strength. It also helps show the size and position of your heart's chambers. An abnormal EKG can be a sign of heart disease or damage.
 
        
             
        
        
        
Answer:
oxygen and hydrogen had equal electronegativity.the covalent bond of water molecules would not be polar,and water molecules would not form hydrogen bonds with each other
Explanation:
explanation was been given in the answer
 
        
             
        
        
        
<span>The person can prepare by eating the right food, exercise, hydration of self and condition oneself for the incoming adventure like extreme.  And also the human body systems respond to changes in the external environment, the nervous system and hormones enable us to respond to external changes. </span>
        
                    
             
        
        
        
The answer is an open system
        
             
        
        
        
C I think is the answer but idk