The highlighted word means 'recklessness'.
Option D is correct. 'Foolishness', in this case, is close in meaning to 'recklessness'. Thus, it is the correct answer.
Options A, B and C are incorrect. They do not have the required meaning.
'Exhaustion' means 'Condition of being tired', 'Obstinacy' means 'stubbornness' and 'Sickness' means 'condition of being ill'.