He was the only reckless worker in the entire staff.

Answer: Option B

Bold : (of a person, action, or idea) showing a willingness to take risks; confident and courageous.
Rash : acting or done without careful consideration of the possible consequences; impetuous.
Courageous : not deterred by danger or pain; brave.
Daring : (of a person or action) adventurous or audaciously bold.
Reckless : heedless of danger or the consequences of one's actions; rash or impetuous.

Synonym of Reckless is Rash