Why was the confederation congress unable to control inflation?

It could not regulate prices, is the right answer.

Explanation:

The Congress of the Confederation was the ruling body of the U.S. that which was established by the Articles of confederation. It was a unicameral assembly with a parliamentary and executive role. This congress was formed of representatives elected by the legislatures of the various states. However, the power given to Congress following this arrangement was very limited. The National government under the Articles of Confederation had no power to levy taxes and some other significant powers. Accordingly, in long-term it could not regulate prices which led to inflation.

Explanation:

It is A. Modern forms of transportation are more convenient.