Definition: You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.
Input: Sentence1: I need a train from Cambridge as well. Sentence2: What time does the 15:51 train arrive? Sentence3: I'm looking for a restaurant called The Nirala. Can you tell me where it is? Sentence4: Sure! What is your destination? Sentence5: Yes as close to 16:45 as possible, book for 2 people please Sentence6: It leaves at 15:00 and gets there at 15:51, sorry for any confusion. Sentence7: thank you and enjoy your stay in our city! Sentence8: It's located at 7 Milton Road Chesterton. Would you like me to book a table? Sentence9: You're all set! Your reference number is QMY8NA1T . Do you need anything else? Sentence10: Would you like me to book the 15:51 train? Sentence11: Okay there are 6 trains that match. Shall I complete a booking? Sentence12: Could you please book a table for 2 at 14:45 on Wednesday Sentence13: I have booked tickets for 2 people, and your reference number is UBY652ER . Anything else I can do for you? Sentence14: I am going to london kings cross on saturday Sentence15: Thank you, that's all for now. Sentence16: The train needs to arrive by 16:45 Sentence17: I have a train that leaves at 5:00 on Saturday. Would you like me to book it for you? Sentence18: Yes please book that train for me. Question: Who has spoken the sentence 4? (A) User (B) System
Output:
Answer: (A) User