You are presented with the question "what is it when a gill converts from oxygen in water into oxygen in blood?" and the following answer choices: 
- fertilization occurs
 - prolactin release
 - preventing heat transfer
 - first step of respiration
 - last step of digestion
 - flow of electrons
 - death
 - fish

Now knowing that breathing is when a gill converts from oxygen in water into oxygen in blood and many people confuse breathing with respiration, but breathing is just the first step of respiration, choose the best answer.


 

    first step of respiration     