Possible Clues:

• 'Like, duh!'
• "Well, duh!"
• "Duh!"
• "No duh"
• 'Duh!,' in modern slang
• "Uh, duh!"
• 'Um, of course!'
• "Duh!," in modern slang
• "Duh," in modern slang
• Curt "Duh"