Given the task definition and input, reply with output. You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.

Sentence1: The Warkworth House is a guesthouse in the East, it's moderately priced and rated 4 stars. I would love to assist you in booking a room if you would like? Sentence2: There are 5 parks in town. Did you have a certain area you prefer? Sentence3: It's actually not a museum, but considered an architecture attraction. Were you interested in a specific type of attraction? Sentence4: Cambridge university botanic gardens is a beautiful park. Its located at bateman street, costs 4 pounds to get in. Phone 01223336265, cb21jf. Will you need transportation? A train, taxi or bus? Sentence5: have a good day Sentence6: No, Is that a museum or a church. Sentence7: Oh, I suggest my favorite! It's Holy Trinity Church, beautiful architecture, and it's located on Market Street. It's free. Would you like their phone number? Sentence8: I have you at the Warkworth house. Would you like to change the reservations? Sentence9: i am looking for somewhere to go in the centre of Cambridge Sentence10: I think we would like it to be in the centre of town please. Sentence11: Yes your reference number is 53LJQ4H6 . Sentence12: No. That's perfect! Thanks for your help. Good bye. Sentence13: Yes, please. Can you reserve a room for Monday for 5 people, 3 nights? Sentence14: no. also find me a hotel by the name warkworth house Sentence15: Actually, I will need to book lodgings as well. Sentence16: Thanks! Can you suggest to me something to visit that isn't a church or architecture? Maybe a museum or a park? Question: Who has spoken the sentence 15? (A) User (B) System
Answer: (B) System