The given word 'adversity' means 'an unfavourable fortune or fate'.
From the options, Option C: 'misfortune' best expresses the meaning of the given word. Hence option C is correct.
Option A: 'Failure' means 'a lack of success'.
Option B: 'Helplessness' means 'unable to help oneself', 'weak or dependent'.
Option D: 'Crisis' means 'a condition of instability or danger'.
These words do not mean the same as the given word, hence options A, B and D are incorrect.