Explanation:

- Store of Value: In a barter system, there's difficulty in storing wealth because not all goods keep their value over time.

- Double Coincidence of Wants: Barter requires both parties to have what the other wants, making exchanges cumbersome.

- Unit of Account: A barter system lacks a common measure to value goods and services, complicating transactions.

- Unemployment: Barter does not directly relate to employment rates. Unemployment is chiefly an economic issue, not a flaw in the barter system.

- Correct Answer: Unemployment