The correct option is B respectful
The word 'derisive' refers to expressing contempt or ridicule.
Option A, enthusiastic refers to having or showing eager and intense enjoyment.
Option B, respectful refers to feeling or showing deference and respect.
Option C, deprecatory refers to expressing disapproval.
Option D, encouraging refers to giving someone support or confidence.
Thus, according to the meaning, the word 'respectful' is the opposite of the word 'derisive'.