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 31-year-old G2 P1 woman gives birth at 38 weeks gestational age to a male infant. However, the placenta cannot be delivered, and there is extensive hemorrhage. She undergoes emergent hysterectomy, and the gross appearance of the uterus is shown here. Which of the following is the most likely diagnosis? <image 1> 
A. Abruptio placenta
B. Placenta accreta
C. Chorioamnionitis
D. Twin placenta
E. Partial mole

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 31-year-old G2 P1 woman gives birth at 38 weeks gestational age to a male infant. However, the placenta cannot be delivered, and there is extensive hemorrhage. She undergoes emergent hysterectomy, and the gross appearance of the uterus is shown here. Which of the following is the most likely diagnosis? <image 1> 
A. Abruptio placenta
B. Placenta accreta
C. Chorioamnionitis
D. Twin placenta
E. Partial mole

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