Possible Clues:

• Really, could they be one's unconscious thoughts? (3,3'1,3)
• 'Really?!'
• 'How astonishing,' one thinks
• The solver is speechless? Well I never
• ''Is that so?''
• "Gosh!," to a mime?
• Conversation filler
• 'Do tell!'
• Ironic response to an obvious remark