Answer:
C. An explanation of the natural world.
Step-by-step explanation:
'The Myths and Legends of Ancient Greece and Rome' is a book written by E. M. Berens. The book consists of mythology and legends of Greece and Rome.
In the given excerpt about the 'introduction to Selene', Berens is explaining about the natural world. In myths, the natural world were personified by gods. In the given text, Helios represents the sun and Selene, the moon, which is sun's sister. Berens is describing the night time.
Therefore the correct answer is option C.