Final answer:
Barter was a trade system used for several thousand years before the introduction of coins around 650-600 B.C.E. in Lydia, making none of the provided options (a. 100 years, b. 500 years, c. 1,000 years, d. 2,000 years) completely accurate.
Step-by-step explanation:
Barter was the main form of trade for many years before the invention of money. This practice of trading one good or service for another, such as exchanging chickens for newspapers, has existed since the beginning of human societies. However, barter proved to be impractical for large-scale and complex transactions, which led to the development of money as a means of exchange that could be used at any time. The first coins were minted in Lydia around 650-600 B.C.E., marking the transition to money-based economies.
To address the student's question, barter as a dominant economic system lasted far beyond the timeframes of 100, 500, or even 1,000 years. With coins appearing around 650-600 B.C.E., and the practice of barter existing long before then, it is reasonable to infer that barter was used for several thousand years.