The Molecular Explanation for Narcolepsy Is That

The molecular explanation for narcolepsy is that

A) certain brain cells have many extra orexin/hypocretin receptors, so that the cell receives too many messages to sleep.
B) the orexin/hypocretin receptor is missing, abnormal in structure, or unable to move to the surface of certain brain cells, blocking signals to stay awake.
C) a gene is missing in chromosome 6 that encodes the protein narcoleptin.
D) a viral infection activates genes that promote sleep.
E) four key genes are overexpressed.