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>Ammonia reacts with oxygen to yield nitrogen and water,<image 1>,Given this chemical equation, as well as the number of moles of the reactant or product indicated below, determine the number of moles of all remaining reactants and products:. 3.0 mol O2
A. 4.0 mol of NH3,3.0 mol of N2,6.0 mol of H2O
B. 4.0 mol of NH3,1.0 mol of N2,6.0 mol of H2O
C. 4.0 mol of NH3,2.0 mol of N2,6.0 mol of H2O

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
C
Ammonia reacts with oxygen to yield nitrogen and water,<image 1>,Given this chemical equation, as well as the number of moles of the reactant or product indicated below, determine the number of moles of all remaining reactants and products:. 3.0 mol O2
A. 4.0 mol of NH3,3.0 mol of N2,6.0 mol of H2O
B. 4.0 mol of NH3,1.0 mol of N2,6.0 mol of H2O
C. 4.0 mol of NH3,2.0 mol of N2,6.0 mol of H2O

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