Answer: Option C
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.
Stupid : having or showing a great lack of intelligence or common sense.
Gentle : having or showing a mild, kind, or tender temperament or character.
Vague : of uncertain, indefinite, or unclear character or meaning.
Docile : ready to accept control or instruction; submissive.
Synonym of Docile is Gentle