Detailed Instructions: You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.
Q: Sentence1: We have 24 guesthouse options. Would you like to narrow it down by area, price, star or parking and internet availability? Sentence2: i want to leave after 19:45 Sentence3: Hmm, can you double check? I would be departing from Bishops Stortford and going to Cambridge for Saturday. Sentence4: Yes please make sure the guesthouse has internet and please provide me with the address and phone number. Sentence5: I want a train leaving on saturday. Sentence6: Where are you departing from, and what is your destination? Sentence7: There are no trains leaving from that location. Sentence8: Of course! I have found 10 trains departing from Bishops Stortford towards Cambridge. Do you have a preferred time to leave or arrive by? Sentence9: Thank you. So what do you have for guesthouses? Sentence10: Can you please provide the price and travel time. I am also looking for a cheap guesthouse in the east with a 4 star rating. Sentence11: 8.08 pounds per ticket and the ride is 38 minutes Sentence12: Train TR1382 leaves at 21:29 and arrives by 22:07, would you like me to book that for you? Sentence13: I am departing from bishops stortford and I would like to go to cambridge. Sentence14: I found the a and b guest house. the address is 124 Tenison Road postcode cb12dp. The phone number is 01223315702. May I book it for you? Sentence15: I hope you enjoy your stay! Sentence16: No that's all, thanks! Question: Who has spoken the sentence 15? (A) User (B) System
A:
Answer: (B) System