The right answer is D. plasticity
Brain plasticity describes the ability of the brain to reshape its connections according to the environment and the experiences of the individual.
From the fetal life, connections between neurons are put in place. Later, after birth, some connections are preserved and others disappear.
The cerebral plasticity is at work during the apprenticeships which require the reworking of the nervous circuits. This is when some connections are reinforced between neurons (synapses). Indeed, the brain is not immutable. On the contrary, it evolves throughout life.
Cerebral plasticity is also possible thanks to undifferentiated cells that can replace accidentally destroyed neurons. For example, in the rat, if vibrisses (whiskers playing a sensory role) are removed, the organization of neurons in the brain is changed. The disappearance of a vibrissa leads to the reorganization of the somatosensory cortex.