Answer:
The correct answer would be option C, The amount of grains harvested.
Explanation:
Most civilizations started Writings in order to keep records of things. Cuneiform was one of the most ancient writing system. Sumerians invented this systems in 3500 BCE in Mesopotamia.
Civilizations felt the need to record the amount or number of grains they used to harvest from the fields, in order to have a record of how much amount is being harvested. So from there they developed the Writings and started keeping their records of the grains harvested.