听力原文:W: Hello, this is Sarah speaking. M: This is Hilton clinic. I'm calling to remind you of your biannual checkup at 10:00 on Thursday, July the 16th. W: I'm sorry but I have a previous engagement that day. Could you reschedule it for either July 20th or 21st? I' d like to see Dr. Helen. M: Hold on please. Dr. Helen isn' t available on the 21st, but I can put you in a time with her for 10 a. m. on the 20th. How does that sound? What is the purpose of the man' s call?