Which of the following is a thin middle layer of cranial meninges?

The meninges are three layers of protective tissue called the dura mater, arachnoid mater, and pia mater that surround the brain and spinal cord. The meninges of the brain and spinal cord are continuous, being linked through the magnum foramen. The arachnoid or arachnoid mater is the middle layer of the meninges. In some areas, it projects into the sinuses formed by the dura mater and transfer cerebrospinal fluid from the ventricles back into the bloodstream.