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><image 1> The function of this structure was to
A. Ring bells to summon the faithful to church, as in a bell tower
B. Be a look-out tower for defense purposes, as in a fortress
C. Create a monument to the glory of a ruler, as in a tomb
D. Signal a time to pray, as in a minaret

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
D
<image 1> The function of this structure was to
A. Ring bells to summon the faithful to church, as in a bell tower
B. Be a look-out tower for defense purposes, as in a fortress
C. Create a monument to the glory of a ruler, as in a tomb
D. Signal a time to pray, as in a minaret

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