I think the answer is A.) giving the readers clues about what is next to come:)
Answer:
Loyalty and betrayal are both minor themes linked to the more prominent themes of servitude versus freedom, in the Tempest. ... Antonio betrayed his brother and stole the dukedom of Milan from him while he (Prospero) was studying. Being the loyal man that he is, Prospero did not expect his brother evil grab for power.
Explanation:
Cornerstone for me is a 7/10 and the other one a for sure 9/10 :)
The correct answer should be an Atlas.
Atlases are huge books filled with maps, most commonly political and geopolitical maps.