Fact 1: Blood pH may become unbalanced if the rate of breathing is too fast or too slow.

Fact 2: For instance, the normal pH of human blood is maintained at 7.4.

Given the two facts above, answer the question "What may become unbalanced if the rate of breathing is too fast or too slow?" with the following options: 
- normal eating
 - normal human blood
 - cigarettes
 - normal skin
 - Veins and arteries.
 - Chemical energy
 - kinetic energy
 - normal studying


 

  normal human blood       