Compare humans inhaling and exhaling to how gills work. Humans | Fish |
Inhaling:
Exhaling

Explanation:

Gills and lungs are the two types of respiratory systems that occur in vertebrates.  

Their main function is to facilitate gas exchange.  

useful link :

https://pediaa.com/what-is-the-difference-between-gills-and-lungs/#:~:text=The%20main%20difference%20between%20gills,while%20mostly%20tetrapods%20use%20lungs.

answer; i believe its (ovulation);