Q: You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.
Sentence1: I'm very sorry a and b guest house does not have availability for your request. Would you like to try a shorter stay or a different day? Sentence2: Sure, what day will you be staying and for how long? Any price range? Sentence3: Yes, I will need accommodations for 7 people, for 5 nights. We want to check in Thursday. Sentence4: I have museums, boating excursions, basic entertainments, parks and swimming pools. Any of these spark your interest? Sentence5: Please try for two nights then at minimum from Thursday evening on. We need a guesthouse for 7 people, and I will need the reference number when booked. Thanks! Sentence6: Never mind. That will be all. Sentence7: Hi, what kind of attractions are there in the east? Sentence8: Is there a guesthouse nearby that is rated at least 4/5? Sentence9: The A and B Guest House is close by. It has a 4 star rating and moderate pricing. Would you like me to book it for you? Sentence10: Now I will need to find a hotel for the remainder of my visit. Can you help with that? Sentence11: Try the funky fun house. It's on cherry hinton road. Sentence12: Yes the A and B guesthouse is a guesthouse. Would you like me to book it for you? Sentence13: Okay, I was able to book the questhouse for you for two nights starting on Thursday. The reference number is O4OXDCIW . Is there anything else I can help you with today? Sentence14: What would you recommend? Sentence15: Okay, I hope you have a pleasant stay! Sentence16: That sounds like what I'm looking for. Is it a guesthouse? Question: Who has spoken the sentence 15? (A) User (B) System
A:
Answer: (B) System