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>As shown in the figure, the fixed straight rod at the left end is subjected to a torsion couple, and the torque at sections 1-1 and 2-2 is: <image 1>
A. 12.0kN.m, -3kN.m
B. -2.5kN.m, -3kN.m
C. -2.5kN.m, -3kN.m
D. 2.5kN.m, -3kN.m

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
As shown in the figure, the fixed straight rod at the left end is subjected to a torsion couple, and the torque at sections 1-1 and 2-2 is: <image 1>
A. 12.0kN.m, -3kN.m
B. -2.5kN.m, -3kN.m
C. -2.5kN.m, -3kN.m
D. 2.5kN.m, -3kN.m

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