Answer:
C. They lose their gills
Explanation:
They lose their gills but grow lungs
<span>Cardiovascular / Circulatory system: ...Digestive system / Excretory system: ...Endocrine system: ...Integumentary system/ Exocrine system: ...Lymphatic system / Immune system: ...Muscular system/Skeletal system: ...Nervous system: ...<span>Renal system / Urinary system:</span></span>