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>The RB gene encodes the retinoblastoma protein (pRB). Note: As shown in <image 1>, the dephosphorylated pRB protein is active in G1 phase. pRB binds to the transcription factor E2F and prevents E2F mediated G1->S transition. The Cyclin D-Cdk4 complex produced during G1, phosphorylates and thereby inactivates pRB. This allows the cell to enter S phase. The p16 protein inhibits the Cyclin D-Cdk4 complex. In which process are the proteins encoded by the target genes of E2F most likely to function? 
A. DNA replication
B. RNA stabilization
C. Splicing
D. Transcription
E. Translation

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
A
The RB gene encodes the retinoblastoma protein (pRB). Note: As shown in <image 1>, the dephosphorylated pRB protein is active in G1 phase. pRB binds to the transcription factor E2F and prevents E2F mediated G1->S transition. The Cyclin D-Cdk4 complex produced during G1, phosphorylates and thereby inactivates pRB. This allows the cell to enter S phase. The p16 protein inhibits the Cyclin D-Cdk4 complex. In which process are the proteins encoded by the target genes of E2F most likely to function? 
A. DNA replication
B. RNA stabilization
C. Splicing
D. Transcription
E. Translation

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