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

Sentence1: The postcode is CB58BS. Can I help you find anything else? Sentence2: Can you tell me what their star rating is? Sentence3: I need something in the south and free parking. Sentence4: I will be in the centre of cambridge. I am looking for any type of attraction involving architecture. Sentence5: You're very welcome, I'm glad that I could help. I hope that you enjoy your stay! Goodbye. Sentence6: Of course! They are a 3-star establishment. Would you like me to go ahead and book that for you? Sentence7: thats it, thanks! Sentence8: Bridge Guest House was available for 2 nights. Your reference number is ULWMFZAX . What else can I do for you today? Sentence9: I'm sorry. There is no availability. Would you like to try different dates or another hotel? Sentence10: I'd recommend All Saints Church on Jesus Lane. Did you need help with anything else? Sentence11: I would recommend the Bridge Guest House based on your criteria. Would you like me to book you a room? Sentence12: There are 33 places to stay, do you have any requirements? Sentence13: How about just 2 nights instead? Sentence14: yes, 7 people 4 nights starting Wednesday. Sentence15: I need a place to stay. Sentence16: Can you give me the postcode for that? Question: Who has spoken the sentence 4? (A) User (B) System
Answer: (A) User