You are presented with the question "What may become unbalanced if the rate of breathing is too fast or too slow?" and the following answer choices: 
- normal eating
 - normal human blood
 - cigarettes
 - normal skin
 - Veins and arteries.
 - Chemical energy
 - kinetic energy
 - normal studying

Now knowing that blood pH may become unbalanced if the rate of breathing is too fast or too slow and for instance, the normal pH of human blood is maintained at 7.4, choose the best answer.


 

  normal human blood       