What Is a Commodity Standard

What is a commodity standard?

A) A widely accepted model for the production of goods.
B) An agreement on trade that sets the standard for the exchange of goods.
C) When a government uses a paper currency whose value is close to a universal standard unit.
D) When a government uses a good with a value of its own as the basic measure of trade.
E) When governments use a good with a value of its own as the basic underlying monetary unit.