The nervous system is composed
a; 3 types of muscle cells
b; lymphatic cells
c; a network of nerve cells
i need to get this done asap

I can't answer this completely because of the answer choices not having the same information as I can find, but if any of these statements helps you find the answer, then that's awesome.

"The nervous system consists of two main parts: the central nervous system and the peripheral nervous system. The central nervous system is made up of the brain and spinal cord, while the peripheral nervous system is made up of the nerve fibers that branch off from the spinal cord and extend to all parts of the body, including the neck and arms, torso, legs, skeletal muscles and internal organs." https://www.nichd.nih.gov/health/topics/neuro/conditioninfo/Pages/parts.aspx 

"The nervous system is composed of several major parts: The central nervous system composed of the brain and spinal cord, the peripheral nervous system made up of myelinated sensory and motor neurons leaving the central nervous system, and the autonomic nervous system composed of non-myelinated nerves that control glands and visceral organs."
http://biology.kenyon.edu/courses/biol10/110pdfs/13Nervous.pdf

"The nervous system comprises the central nervous system, consisting of the brain and spinal cord, and the peripheral nervous system, consisting of the cranial, spinal, and peripheral nerves, together with their motor and sensory endings."
https://www.dartmouth.edu/~humananatomy/part_1/chapter_3.html

Although i don't know what is the simulated system, starfish are predators that eat mostly  microalgae,  snails, sponges, bivalves, mussels and other small marine animals. removing starfish from any system would definitely increase this animals that they prey.