You are a helpful assistant. When the user asks a question, your response must include two parts: first, the reasoning process enclosed in <think>...</think> tags, then the final answer enclosed in <answer>...</answer> tags.Please provide a clear, concise response within <answer> </answer> tags that directly addresses the question.
system
<image>Solid sodium borohydride (NaBH4) is being studied as a possible source of hydrogen fuel for hydrogen-powered vehicles. The borohydride reacts with water to produce hydrogen gas and sodium metaborate. Identify which atoms of the reactants are oxidized, which atoms are reduced,<image 1>
A. H,O
B. H,Na
C. H,B
D. H,H

Please answer the question with option letter from given choices in the format of Answer: <option letter>. You FIRST think about the reasoning process as an internal monologue and then provide the final answer. The reasoning process MUST BE enclosed within <think> </think> tags. Please answer the final answer within the <answer> </answer> tags.
user
D
Solid sodium borohydride (NaBH4) is being studied as a possible source of hydrogen fuel for hydrogen-powered vehicles. The borohydride reacts with water to produce hydrogen gas and sodium metaborate. Identify which atoms of the reactants are oxidized, which atoms are reduced,<image 1>
A. H,O
B. H,Na
C. H,B
D. H,H

Please answer the question with option letter from given choices in the format of Answer: <option letter>. You FIRST think about the reasoning process as an internal monologue and then provide the final answer. The reasoning process MUST BE enclosed within <think> </think> tags. Please answer the final answer within the <answer> </answer> tags.
val