Possible Clues:

• "Like, how did I make THAT mistake?"
• "Anyone can see that"
• 'Well, how obvious!'
• 'That much was obvious'
• 'That's, like, so obvious'
• 'I am such a dope!'
• Head-slapping word
• 'Thank you, Captain Obvious!'
• Word that retains its meaning when preceded by 'no'
• ''C'mon, that's too easy!''