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>Find the minimum spanning tree of the graph G(V, U) of figure 1. Notice that it is an undirected graph.
<image 1>
A. Graph G1 with vertices v1 to v8 and arcs including (v1, v3), (v2, v3) and so on.
B. Graph G2 with vertices v1 to v8 and arcs including (v2, v5) and (v4, v8).
C. Graph G1 with vertices v1 to v8 and arcs excluding (v2, v5) and (v4, v8).
D. Graph G2 with vertices v1 to v8 and no arc connecting A1 and A3.

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
Find the minimum spanning tree of the graph G(V, U) of figure 1. Notice that it is an undirected graph.
<image 1>
A. Graph G1 with vertices v1 to v8 and arcs including (v1, v3), (v2, v3) and so on.
B. Graph G2 with vertices v1 to v8 and arcs including (v2, v5) and (v4, v8).
C. Graph G1 with vertices v1 to v8 and arcs excluding (v2, v5) and (v4, v8).
D. Graph G2 with vertices v1 to v8 and no arc connecting A1 and A3.

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