The venerable professor, known for his ______ wit, could often disarm even the most aggressive debaters with a well-placed, self-deprecating remark.

✓ Correct Answer: Option C

The professor 'disarms' aggressive debaters with 'self-deprecating remarks,' suggesting a pleasant and friendly, rather than sharp or bitter, wit. 'Genial' means friendly and cheerful, fitting this context. 'Acerbic,' 'caustic,' and 'sardonic' imply bitterness.