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

Sentence1: You're welcome. Is there anything else I can help you with? Sentence2: I am looking for a 3 star hotel to stay in. Sentence3: Thank you. What's the travel time? Sentence4: No, that is all I need. Thanks! Sentence5: I reserved Wednesday night at the University Arms Hotel for 5 people. Your reference number is GM90EY8A . Is there anything else? Sentence6: travel time is 47 minutes Sentence7: Lets try just booking it for one night. Sentence8: The hotel should be in the expensive price range. Sentence9: Okay, I've got two that fit the bill. One in the centre of town and one in the south. Do you have a preference? Sentence10: I am very sorry, but I was unable to book a reservation for you. Would you be willing to book a later day or would you be willing to have a shorter stay? Sentence11: I do, yes. I would like to stay in the center of town. I need it to fit five people, for 3 nights, starting Wednesday afternoon. Sentence12: Great! I will need 5 tickets. Sentence13: same day as my hotel booking. Sentence14: You are booked for Train Tr5556, your reference number is JA6WAOJC . Sentence15: I do have a four star hotel in the centre of town, but it is also unable to accommodate your guests for 3 days. Can you adjust your length of stay? Sentence16: Sure I will be able to book you a train, on what particular day will you want to travel? Sentence17: Can we book the other expensive 3 star hotel for one night starting on wednesday? Sentence18: I apologize. One night is not working either. There are guesthouses. Sentence19: How many tickets do you need? Sentence20: There are 6, 3 start hotels in Cambridge. Do you have a preference for the part of town it is located in? Sentence21: No trouble at all, I hope you have a wonderful stay! Sentence22: What about the 4 star hotels? Sentence23: Yes, I also need a train leaving after 18:30 from kings lynn to cambridge. Sentence24: Thank you very much. Question: Who has spoken the sentence 4? (A) User (B) System
Answer: (A) User