The main responsible for the delay among the atrial and
ventricular contractions is the action potential conduction velocity of the AV
node cells. If the atria and ventricles contract simultaneously, atria cannot
give any help in filling the ventricles, which is needed, especially in those
with stiff ventricles as in the elderly. Hence atria have to contract first and
then the ventricles.
 
        
             
        
        
        
Answer:
Mayra should be checked regularly for heart-related problems.
 
        
             
        
        
        
A. Break down sugars to use their energy directly
        
             
        
        
        
Answer:
Carbon Dioxide 
Explanation:
Plant cells respire in the light and the dark, releasing carbon dioxide. 
(brainliest please)