Cerebrospinal fluid: a. is identical in composition to whole blood b. is secreted by the arachnoid villi c. is secreted mostly by the astrocytes cells lining the brain ventricles d. enters the four ventricles after filling and circulating through the subarachnoid space e. is continually formed mostly by the choroid plexuses

e. is continually formed mostly by the choroid plexuses

Explanation:

The clear colorless fluid that protects the brain and spinal cord from injuries and carries nutrients, respiratory gases, and other chemicals is called cerebrospinal fluid. The cerebrospinal fluid circulates through cavities in the brain and spinal cord and in the subarachnoid space around the central nervous system. The networks of the blood capillaries present in the walls of ventricles form choroid plexuses. Specific substances are filtered from the blood plasma by these capillaries and are secreted by ependymal cells to produce cerebrospinal fluid.