Answer:B. Development of agriculture
Explanation: The development of Agriculture during the early human civilisation was the direct cause of specialisation.
During the early civilisation Farmers, Hunters, Animal rearers, fishermen,were able to produce surplus foods, this led people to start developing other connected trades or activities that can help to utilize the Agricultural products. People started getting involved in TRADING the produce,others specialised in CRAFTS, others specialised in the use of ANIMAL SKIN for leathers etc Agriculture was the first activity of the early civilisation and can be tagged as the mother of other forms of trade. especially those connected with food, Furniture, Textiles etc