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>The introduction of the oral contraceptive(OC) in the 1960s provided an additional effective means of family planning, but it also had unanticipated side effects, particularly the susceptibility to thromboembolism. Women taking OC had an increased risk of pulmonary, cerebral, and coronary thrombosis or embolism.A larger case-control study was conducted in the United States between 1976-1978 by Shapiro et al. to explore the relationship between OC use and myocardial infarction(MI) in women under 50 years of age.The age distribution of the MI and control groups and OC exposure among MI patients and controls in each age group were shown in the table below.<image 1> The 95% CI for OR in 25-29 years was
A. (1.29~40.37)
B. (3.48~22.56)
C. (0.51~4.68)
D. (1.28~10.78)
E. (1.16~13.02)

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
The introduction of the oral contraceptive(OC) in the 1960s provided an additional effective means of family planning, but it also had unanticipated side effects, particularly the susceptibility to thromboembolism. Women taking OC had an increased risk of pulmonary, cerebral, and coronary thrombosis or embolism.A larger case-control study was conducted in the United States between 1976-1978 by Shapiro et al. to explore the relationship between OC use and myocardial infarction(MI) in women under 50 years of age.The age distribution of the MI and control groups and OC exposure among MI patients and controls in each age group were shown in the table below.<image 1> The 95% CI for OR in 25-29 years was
A. (1.29~40.37)
B. (3.48~22.56)
C. (0.51~4.68)
D. (1.28~10.78)
E. (1.16~13.02)

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