You are presented with the quiz "what can cause blood pH to become unbalanced?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "blood pH may become unbalanced if the rate of breathing is too fast or too slow" and "aerobic activities are exercises that cause deep breathing and a fast heart rate". 

So, what's the best answer to the question?


 

 aerobic activities          