In the given sentence, the word "obstinate" is used to describe the boy, indicating that he is difficult to manage or control because of his stubbornness. Someone who is obstinate is resistant to changing their opinions, actions, or behaviour.
The word "stubborn" (option B) is the closest in meaning to "obstinate." It refers to a person who is unyielding, determined to do things their own way, and resistant to persuasion or change.