You will be given a definition of a task first, then some input of the task.
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, have a great day! Sentence2: Could we try 2 nights. Sentence3: I don't need tickets right now, but can you tell me the train ID for the 22:58 train, please? Sentence4: I'm sorry, but I was not able to book it. Would you like to try another day or, perhaps, a shorter stay? Sentence5: I am looking for a guesthouse to stay in when I visit next month. Sentence6: Could I book it for 1 person for 3 nights starting Tuesday? Sentence7: Oh sorry I still want to look for a train from Cambridge to Kings Lynn which leaves at 21:15 Thursday. Sentence8: Alright I've found quite a few. How about the acorn guest house? Sentence9: The train is TR3495. Will that be all today? Sentence10: I would recommend Bridge Guest House. It is in the south and has 3 stars with free wifi and parking. Sentence11: That was a success! Your reference number is G8JEZPDW . Is there anything else I can help you with? Sentence12: Does it have 3 stars? I'd like my lodgings to be 3-star rated, please. I'm quite particular. I also will require free parking and Internet. Sentence13: I have two, arrivals of 22:58 and 23:68. Shall I book them? Sentence14: No, that is all, thank you again. Sentence15: You're very welcome. Goodbye! Sentence16: No,that is all thanks. Question: Who has spoken the sentence 4? (A) User (B) System
Output:
Answer: (A) User