The answer is A: Mass extinction.
"Abrupt disappearance of many land and marine species" = extinction of many species.
Answer:
Coelenterates are the first invertebrates to develop a true nervous system.
Explanation:
As the head organ in the body which controls, monitors, supervises and influences the different organ system in the body and of the individual -characteristics, personality, traits, cognition, perception, intelligence, sensation and motor responses. The brain controls the endocrine system by its part, located somwhere in the medial temporal lobe called the hypothalamus, the master gland of the body. The hypothalamus influences every gland secretion and hormonal function that preceeds and proceeds in the body of an organism -growth, drives, sex, survival and etc.
The hypothalamus sends sgnals from the different gland organs in the body that either exhibits or inhibits the activity of that particular gland releasing hormone.
