The correct answer is A. impulsive.
Based on the excerpt, Harry takes action without forethought. If he had thought about his actions, he may have considered that someone could walk in, or he may have heard someone approaching at the door; however, he does not think about what may happen, he simply snatches up the book and parchment on impulse with the intent to throw them into the fire, and he hadn't noticed his uncle was near until he opened the door.
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