What organ system generates the heat needed by warm-blooded animals such as humans?

There are eleven major organ systems are present in human and animals. The organ system that generates the heat needed by warm-blooded animals such as humans is the muscular system. Aside from generating heat, the muscular system facilitates movement and locomotion. It produces body movements, maintains posture, and supports the body. Heat is generated thru muscle contractions and as much as 70% of the body heat is produced in the muscle tissue. 

substitution is the answer in this case

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.