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>See the following phase diagram below, where there are 5 points labeled as (A), (B), (C), (D), and (E), respectively. <image 1> At which point will the substancemce represented by the phase diagram be solely in the solid phase at equilibrium?
A. (A)
B. (B)
C. (C)
D. (D)
E. (E)

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
See the following phase diagram below, where there are 5 points labeled as (A), (B), (C), (D), and (E), respectively. <image 1> At which point will the substancemce represented by the phase diagram be solely in the solid phase at equilibrium?
A. (A)
B. (B)
C. (C)
D. (D)
E. (E)

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