The sentence is an example of a cause and effect reasoning. It helps to stablish the relationship between an event that comes first, and the one that takes place after the former. This type of reasoning provides the necessary information and details to understand why certain events happens as they do.
A work/writing can have many many many different moods.
Mood is the general atmosphere created by the writer, if the writer wanted anger, love, sorrow, etc, he would use "mood" to express the feeling in the characters.
Hope this helps!
•❋Korey❋•
I think it’s the 2nd or 3rd option but not sure exactly which one.