6559. I tried to persuade him to change his mind, but he remained adamant.

✅ The correct answer is option C.
Foolish : lacking good sense or judgement; unwise.

Aggressive : ready or likely to attack or confront; characterized by or resulting from aggression.

Stubborn : having or showing dogged determination not to change one’s attitude or position on something, especially in spite of good arguments or reasons to do so.

Defensive : used or intended to defend or protect.

Adamant : refusing to be persuaded or to change one’s mind.

Synonym of Adamant is Stubborn