The options for this question would be:
a. All the options are correct.
b. The limbic regions of the brain are active during sleep, which could be the source of the emotional content of Tom's dream.
c. Frontal cortices are somewhat deactivated during sleep, which contributes to illogical aspects of dreaming.
d. Neurons were randomly firing, and Tom's sleeping mind attempted to make sense of the chaotic neural activity.
The answer would be letter "a"
