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 23-year-old G2 P1 woman has noted minimal fetal movement in the second trimester. An ultrasound scan at 19 weeks shows hydrops fetalis. A girl infant is born at 32 weeks gestation and is markedly icteric. The microscopic appearance of the placenta is shown here. Laboratory studies show the baby has a Hct of 18%, and an exchange transfusion is performed. Her first pregnancy was uncomplicated and resulted in the birth of a normal girl at term. Which of the following immunologic mechanisms is most likely to produce these findings? <image 1> 
A. Anti-receptor antibody
B. Immune complex formation
C. Complement mediated cell destruction
D. Delayed type hypersensitivity
E. Loss of self tolerance

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
C
A 23-year-old G2 P1 woman has noted minimal fetal movement in the second trimester. An ultrasound scan at 19 weeks shows hydrops fetalis. A girl infant is born at 32 weeks gestation and is markedly icteric. The microscopic appearance of the placenta is shown here. Laboratory studies show the baby has a Hct of 18%, and an exchange transfusion is performed. Her first pregnancy was uncomplicated and resulted in the birth of a normal girl at term. Which of the following immunologic mechanisms is most likely to produce these findings? <image 1> 
A. Anti-receptor antibody
B. Immune complex formation
C. Complement mediated cell destruction
D. Delayed type hypersensitivity
E. Loss of self tolerance

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