A b. c d ??? anyone help me please ?

This is a coral reef ecosystem. many biotic and abiotic factors affect the health of this ecosystem. which set correctly pairs a biotic factor and an abiotic factor?

An organ system consists of a group of organs that performs specific functions necessary for the survival of an organism. humans have eleven different organ systems: integumentary, skeletal, muscular, nervous, endocrine, circulatory, lymphatic, respiratory, digestive, urinary, and reproductive. discuss the function of neurons, the brain and the spinal cord within the human nervous system while explaining the interrelationship of each organ.

What are the formed elements (cell or parts of cell) in blood and what are their functions ?