Used to express your belief that what was said was stupid or extremely obvious

"Oh, you are American, so you speak English" "Well, duh!"

"Oh, sei americano. Ma allora parli inglese" "Beh, sei proprio una volpe!"

"He drives a Ferrari and has a private jet. He must be very rich" "Duh!"

"Ha una Ferrari e un aereo privato: deve essere molto ricco" "Ma va! Oggi hai mangiato pane e volpe"