The correct answer is the Neolithic period.
The Neolithic period is a period in human prehistory distinguished by the original development of agriculture, which enabled the transition from hunting and gathering to more sedentary living. The Neolithic period began around 10,200 years ago in the Fertile Crescent, and spread from there throughout the world.
Stone ‘celts’ (polished axes) are a type of stone tool that was used during the Neolithic period. They were made by polishing a piece of stone into a sharp edge, and were used for a variety of purposes, including cutting wood, clearing land, and hunting.
The discovery of stone ‘celts’ in Bihar is evidence that the region was inhabited during the Neolithic period. The use of stone ‘celts’ suggests that the people of Bihar were engaged in agriculture, as they would have needed to clear land in order to plant crops.
The other options are incorrect because they are not associated with the Neolithic period. The Palaeolithic period is the earliest period of human prehistory, and is characterized by the use of stone tools. The Chalcolithic period is a period of transition between the Neolithic and Bronze Ages, and is characterized by the use of copper tools. The Iron Age is a period of human history characterized by the use of iron tools.