Possible Clues:

• "That's unlikely"
• 'Yeah, sure ...'
• 'Yeah, as if!'
• 'Su-u-u-ure'
• ''Oh, sure''
• 'Yeah, whatever you say'
• Skeptic's snort
• Sarcastic "Yeah, sure!"
• Words accompanying an eye roll
• 'You expect me to believe that?'