Answer:
Personification
Step-by-step explanation:
Personification is when an inanimate object does something that a person can do. For example, in this question, the moon didn't actually sigh, but something must have happened that made the onlookers feel like sighing (overwhelmed, bored, etc.) and the moon is "watching" a lot of the time and is well-known and important, so it was used as an example.