Answer:c. evolutionary
Explanation:A certain behaviour by certain species can either help them survive or can lead to their elimination from existing.
This behaviour of being afraid of the dark was a survival instinct that contributed to them surviving from being eaten by dangerous animals that come out at night .
In the dark they wouldn't be able to suspect danger and would have been vulnerable to protect themselves from such but their fear probably caused them to hide away .
Their survival instinct sheltered them from possible danger that might have eliminated them completely .
