Answer:
a. currency.
Explanation:
The exchange system, which is considered the first form of commerce, was local. This means that only people from a given community made these exchanges. Each family had a certain skill: fishing, agriculture, livestock, etc. To guarantee sustenance and good productivity, this ancestry was only concerned with this single task. In the end, they produced more than they consumed, and thus began to stockpile. But the products spoiled, and in addition, the house needed other items besides those that were made by them. Hence the need for exchange arose. This system allowed people not to suffer from the waste of their goods and still obtain others, cultivated or raised by different families.
As the exchanges were direct and without specific prices, bargaining was the way to get a good deal.
However, over time, this traditional system of exchange has been replaced by a more sophisticated system that depended on currencies and that looks more like the trade we know today.