Final answer:
Out of the three options provided, the pia mater is the meninx that is most closely associated with the contours of the spinal cord. This layer directly contacts and covers the central nervous system, following all convolutions and matching the contours of the spinal cord.
Step-by-step explanation:
The meninx that is closely associated with the contours of the spinal cord is the pia mater. The pia mater is the innermost layer of the meninges – a series of membranes that cover the central nervous system (CNS), which includes the brain and the spinal cord. Unlike the dura mater, a robust protective layer, or the arachnoid mater, a loose sac-like layer, the pia mater is a thin, gentle covering. The pia mater directly contacts and covers the brain and the spinal cord, following every convolution of the CNS, lining the inside of the sulci in the cerebral and cerebellar cortices, and matching the contours of the spinal cord.
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