You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.

Sentence1: I would like it at 15:00 on the same day. Sentence2: I need to catch a train in London King's Cross to ride into Cambridge. Sentence3: Very well, I've booked you at Restaurant One Seven for 4 people at 15:00 on Monday. Would you like the booking reference number? Sentence4: Sorry about that, the reference number is 5F63AFCU Sentence5: Thank you for your time. Sentence6: I have booked your train. London King's Cross to Cambridge at 13:17 on Monday. Sentence7: I'm glad I could help you today. Have a great trip. Goodbye. Sentence8: Thank you! That sounds excellent! I am also craving British food. Are there any moderately priced British restaurants there? Sentence9: Not really, I'll just need to book it for the same day for 4 people. Sentence10: What time would you like the reservation? Sentence11: I want to leave on Monday after 12:45. Sentence12: I do apologize, train TR3194 would leave at 13:17, NOT 14:12. The travel time would be 51 minutes. Would you like me to book this train for you? Sentence13: I can help with that. What day and time were you looking to depart? Sentence14: There is a train available on 14:12. Sentence15: Yes can you please book it. Sentence16: Yes of course I want the reference number! Why wouldn't I! Sentence17: We have four in the centre area and one int he west, any preferences? Sentence18: That is fine. Can you provide the arrival time, train ID, and travel time. Question: Who has spoken the sentence 1? (A) User (B) System
Answer: (B) System