​Why Are People Unconscious Most of the Time While They

​Why are people unconscious most of the time while they are asleep?

A) Neurons in most areas of the brain stop producing action potentials.
B) ​Except for extremely strong stimuli, the sense organs stop sending messages to the brain.
C) ​Inhibitory synapses block the spread of messages from one brain area to another.
D) ​Action potentials in the brain slow to approximately one-third their usual speed.