Answer: Due to reticular formation activation system
Step-by-step explanation:
Reticular formation activation system is the system which is present in brain as small-sized pencil responsible for regulation of information between sensory system and mind.It invokes wakefulness in a person or sleep-wake transition through sending sensed information to make conscious .
According to the question, reticular formation activation system is responsible due to which parents got awake from sleep when fire broke as they received sensory information because it was their duty to protect children from fire whereas children are asleep as they are having sound and restful sleep through information sensed stimuli as parent will take care of the condition.