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 29-year-old G3 P2 woman has an uncomplicated pregnancy, and an ultrasound scan at 18 weeks gestation is completely normal. At 37 weeks she has the sudden onset of pelvic pain accompanied by passage of blood per vagina. Her membranes have not ruptured nor is she having labor contractions. Fetal monitoring reveals that the baby is in distress, and an emergent cesarean section is performed. The gross appearance of the placenta is shown here. Which of the following is the most likely diagnosis? <image 1> 
A. Ectopic pregnancy
B. Placenta previa
C. Placenta accreta
D. Molar pregnancy
E. Abruptio placenta
F. Pregnancy-induced hypertension

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
E
A 29-year-old G3 P2 woman has an uncomplicated pregnancy, and an ultrasound scan at 18 weeks gestation is completely normal. At 37 weeks she has the sudden onset of pelvic pain accompanied by passage of blood per vagina. Her membranes have not ruptured nor is she having labor contractions. Fetal monitoring reveals that the baby is in distress, and an emergent cesarean section is performed. The gross appearance of the placenta is shown here. Which of the following is the most likely diagnosis? <image 1> 
A. Ectopic pregnancy
B. Placenta previa
C. Placenta accreta
D. Molar pregnancy
E. Abruptio placenta
F. Pregnancy-induced hypertension

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