duh 
/ˈdʌ, usually with a prolonged vowel/ interjection
/ˈdʌ, usually with a prolonged vowel/ interjection US, informal 1 — used in an angry or annoyed way to show that something just said is already known or is obvious ▪ “It sure is dark out.” “Duh, it's the middle of the night.” ▪ “You have to turn the key to start the car.” “Well, duh.” [=I know that] 2 — used to show or pretend that you do not know something ▪ “Why didn't you leave earlier?” “Duh, I don't know.”
