Drops ya like a sack of potatos. (Aka undermines)
The correct option is C, Essential.
The definition of core is the central or most important part of something or something therefore considered necessary.
The definition of essential is something absolutely necessary; extremely important. Therefore the closest synonym to core is essential :)
A brief summary: Talks about animals that are nocturnal, explains why some animals are nocturnal and not diurnal, how they see at night, how they communicate, and where they go during the day.
I got some of this information from fab.lexile.com
Mandy failed to beat her final opponent, yet she practiced karate every day