context: Archaeological investigation has found evidence of irrigation in areas lacking sufficient  natural rainfall to support crops for rainfed agriculture. The earliest known use of the technology dates to the 6th millennium BCE in  Khuzistan in the south-west of present-day Iran.[4][5]
question: What is the earliest known example of irrigation?
answers.text: 6th millennium BCE in  Khuzistan dates to the 6th millennium BCE in  Khuzistan in the south-west of present-day Iran