Option 1: Dholavira - The terracotta of `plough` was not found at Dholavira.

Option 2: Banawali - The terracotta of `plough` was found at Banawali. This discovery is significant because it suggests that the Harappans were using advanced agricultural techniques such as plowing the land.

Option 3: Harappa - The terracotta of `plough` was not found at Harappa.

Option 4: Lothal - The terracotta of `plough` was not found at Lothal.

Therefore, the correct answer is option 2, Banawali, where the terracotta of `plough` was found. This discovery provides evidence of the Harappans engaging in agriculture and using tools like plows to cultivate their land.