You are shown a conversation between a user and system. Identify who has spoken the indicated sentence based on the conversation.
Q: Sentence1: Are there any cheap restaurants in the centre that I can try? Sentence2: No thank you. I need to find a train leaving Cambridge after 16:30. Sentence3: I have 5 different trains leaving Cambridge on Friday evening, which destination do you prefer: kings cross or liverpool street? Sentence4: Sure! The Golden House is a Chinese restaurant that's located at 12 Lensfield Road, City Centre. Would you like a table reserved? Sentence5: You're very welcome. Good-bye. Sentence6: Booking was successful, the total fee is 12.8 GBP payable at the station. Reference number is : L9DAX54Q . Can I help you with anything else today? Sentence7: 17:21 sounds fine. Please make a booking for 1 person and let me know the reference number. Sentence8: I actually need to go to stevenage. Sentence9: There are trains leaving Cambridge every two hours starting at 17:21 and arriving in Stevanage one hour later. Which time do you prefer? Sentence10: I would like to leave on Tuesday, please. Sentence11: Thank you goodbye Sentence12: can you suggest one, I am not picky, just need the type and address Sentence13: What day do you need to leave? Sentence14: Yes, there are many. What type of cuisine are you interested in? Question: Who has spoken the sentence 7? (A) User (B) System
A:
Answer: (B) System