The structure of the spinal cord can be described as(1) composed of thirty-one segments(2) having a cervical enlargement, lumbar enlargement, and two deep longitudinal grooves(3) a central core of gray matter that is surrounded by white matter(4) having gray matter that is composed of myelinated nerve fibers

(1) composed of thirty-one segments

Explanation: Spinal Cord Nerve Branches contains 31 segments pairs of spinal nerves. Each nerves are form,from both combination of posterior and anterior roots.

the answer is d (apex) good luck : ))

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