O Repaying of loans was not closely monitored. Currency varied widely from state to state.
O The dollar bill was introduced.
O The Second Bank of the United States was established.

Currency varied widely from state to state.

Explanation:

Here's the complete question:

What occurred during the Free Banking Era?

a. Currency varied widely from state to state.

b. Repaying of loans was not closely monitored.

c. The Second Bank of the United States was established.

d. The dollar bill was introduced.

The Free Banking Era occured between 1837 - 1863. During this period, states issued their banknotes and it was a period that the state-chartered banks dominated.

Due to the fact that the states were privileged to issue their own banknotes, this led to variation in currency from states to states.