You are presented with the question "what is regulated by breathing?" and the following answer choices: 
- thirst
 - air pressure
 - blood flow
 - body water
 - Energy
 - Chemical energy
 - Decibels
 - kinetic energy

Now knowing that blood pH may become unbalanced if the rate of breathing is too fast or too slow and breathing is regulated to keep as normal as possible arterial blood pH and PO2, choose the best answer.


 

   blood flow      