Mary didn't go to John's birthday party because she ______. [ ]

A. wasn't invited

B. didn't invite

C. isn't invited

       罗伯特是德国著名的医生。有一天，他为国王看病。国王说：“你给我看病，不能像看别的病人那样！”罗伯特非常平静地回答说：“请原谅，陛下，在我眼里，病人都是国王。”医生答话的的言外之意是                                                                                             。