Myelin is important because it:

A) connects the two halves of the brain.
B) compensates for loss of brain function due to injury.
C) promotes regular childhood sleep patterns.
D) speeds up the transmission of neural impulses.

Myelin acts as an insulating layer around neurons, which allows for faster transmission of neural impulses by preventing signal leakage. This is especially important for complex cognitive processes such as learning, memory, and decision-making, making option D the best choice.