Possible Clues:

• ''Who's there?'' answer
• Formal identification
• Formal response to 'Who's there?'
• Formal reply to 'Who's there?'
• Formal response at the door
• Formal "Who's there?" response
• Formal answer to "Who's there?"
• Formal response to ''Who's there?''
• Formal "Just me"
• Formal response to 'Who goes there?'