The correct option is A Prosperity
The word 'adversity' refers to a difficult or unpleasant situation.
Option A, prosperity refers to the state of being prosperous.
Option B, curiosity refers to a strong desire to know or learn something.
Option C, animosity refers to strong hostility.
Option D, sincerity refers to the absence of pretence, deceit or hypocrisy.
Thus, according to the meaning, the word 'prosperity' is the opposite of the word 'adversity'.