6381. Quite unabashed, he began his scholarly lecture on what was obvious to everyone.

✅ The correct answer is option A.
Unashamed : expressed or acting openly and without guilt or embarrassment.

Unimpressed : feeling no admiration, interest, or respect.

Unnerved : make (someone) lose courage or confidence.

Unchecked : (especially of something undesirable) not controlled or restrained.

Unabashed : not embarrassed, disconcerted, or ashamed.

Synonym of Unabashed is Unashamed