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>Which feature(s) of this developing embryo are already established at the stage shown in <image 1>
A. segmentation
B. head-tail orientation
C. limb placement
D. type of symmetry
E. limb placement and segmentation
F. segmentation, type of symmetry and head-tail orientation
G. segmentation, head-tail orientation and limb placement
H. type of symmetry and head-tail orientation
I. segmentation and head-tail orientation

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
F
Which feature(s) of this developing embryo are already established at the stage shown in <image 1>
A. segmentation
B. head-tail orientation
C. limb placement
D. type of symmetry
E. limb placement and segmentation
F. segmentation, type of symmetry and head-tail orientation
G. segmentation, head-tail orientation and limb placement
H. type of symmetry and head-tail orientation
I. segmentation and head-tail orientation

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