Concept:Money used during the barter era took the form of everyday goods that people agreed to accept in exchange.
Explanation:Before coins and notes existed, trade was done through the barter system.
However, direct exchange of goods was often difficult.
So, certain widely accepted commodities were used as a medium of exchange.
Examples include salt, cowrie shells, cattle, grains, and precious metals.
These items had value in themselves and were generally acceptable by all parties.
This type of money is called commodity money.
Answer:D. commodities