Final answer:
The correct answer is A .The middle layer of the meninges, which covers the brain and spinal cord, is called the arachnoid mater. It is characterized by a web-like appearance and plays a critical roles.
Step-by-step explanation:
The meninges are a series of protective coverings that encase the central nervous system (CNS), which includes the brain and spinal cord.
The middle layer of the meninges is called the arachnoid mater, and it is named for its distinctive spider-web-like appearance.
This layer is crucial as it defines a sac-like enclosure around the CNS and is involved in the circulation and drainage of cerebrospinal fluid (CSF), providing a vital protective environment for the brain and spinal cord.