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>A researcher recorded systolic blood pressure and body mass index in 10 men aged 35-45 years, and the data are shown in the table below. <image 1> Linear regression analysis with systolic blood pressure as the dependent variable and body mass index as the independent variable yielded a regression coefficient of b = 1.648, SS back = 1044.352, and SS total = 1,878.400. The coefficient of determination was 
A. 0.444
B. 0.556
C. 1.799
D. 2.716

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
B
A researcher recorded systolic blood pressure and body mass index in 10 men aged 35-45 years, and the data are shown in the table below. <image 1> Linear regression analysis with systolic blood pressure as the dependent variable and body mass index as the independent variable yielded a regression coefficient of b = 1.648, SS back = 1044.352, and SS total = 1,878.400. The coefficient of determination was 
A. 0.444
B. 0.556
C. 1.799
D. 2.716

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