The answer is alveoli, there the only structures.
Hope this helps! Have a BLESSED day! :-)
Yes because <span>A </span>habitable zone<span> (HZ) in astronomy is a region of space where conditions are best for life to form as on Earth. Planets in these areas are the most likely to have extraterrestrial life. The </span>habitable zone<span> may also be called the "life zone", "comfort zone", "green belt" or "Goldilocks zone".</span>