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>Maximize 3∑i=1 ri
 Subject to: Si  1 = 3Si    d1 i = 1, 2, 3, Si ≧ di ≧ 0 where r1 = 3d1 r2 = 3d2 r3 = 3d32
<image 1>
A. d1* = S1 and d2* = 0 and d3* = S3
B. d1* = 0 and d2* = S2 and d3* = 0
C. d1* = S1 and d2* = S2 and d3* = 0
D. d1* = 0 and d2* = 0 and d3* = S3

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
A
Maximize 3∑i=1 ri
 Subject to: Si  1 = 3Si    d1 i = 1, 2, 3, Si ≧ di ≧ 0 where r1 = 3d1 r2 = 3d2 r3 = 3d32
<image 1>
A. d1* = S1 and d2* = 0 and d3* = S3
B. d1* = 0 and d2* = S2 and d3* = 0
C. d1* = S1 and d2* = S2 and d3* = 0
D. d1* = 0 and d2* = 0 and d3* = S3

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.
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