Answer:
A. money
Step-by-step explanation:
Under the Articles of Confederation, each state had its own form of currency, in other words, its own money. This made trade more difficult because transactions had to be converted from the currency of the seller state, to the currency of the buyer state.
The U.S. Constitution, which replaced the Articles of Confederation, solve this problem by allowing the Federal Government to issue a single currency for the entirety of the American territory.