The correct answer is D. Both think that in Europe he would be an oddity who would bring them wealth or favor.
In Act 2, Scene 2, Trinculo sees Caliban and perceives him like a monster. People in England would pay good money to see such a freak, says he. Then, when Stephano enters, he also notices Caliban's weird looks, and thinks that he would be a gift worthy of an emperor. Stephano gives him alcohol in order to tame him, reckoning that he would cost even more if he were tame.
Observing nature is great because you can learn so much about the world around you.
Obseving the earth can help you make new discoveries