Gray matter
a) replaces white matter in middle childhood.
b) consists largely of myelinated nerve fibers.
c) increases steadily throughout childhood and adolescence.
d) declines as synaptic pruning and death of surrounding neurons proceed.

D) declines as synaptic pruning and death of surrounding neurons proceed.

Explanation:

Gray matter -

It is one of the main component of the central nervous system , which is composed of  capillaries , synapses , glial cells , neuropil and neuronal cell bodies .

The grey matter have many cell bodies and fewer myelinated axons , in comparison to the white matter .

The color of grey matter is light grey with hints of yellow and pink which are due to the blood capillaries and the neuronal cell bodies .

The correct option regarding grey matter is ( d ) .

your answer is "the 1950's"