What financial development during this era greatly expanded the amount

What financial development during this era greatly expanded the amount of money in circulation but also made banking much riskier?

A) the printing of paper currency, bank notes, that were backed by gold and silver deposits
B) banks making loans to businessmen and investors and collecting interest on those loans
C) the entrance into the banking profession of political cronies, rampant speculators, and unrepentant criminals
D) the issuing of bank notes, not only on the gold and silver deposits the banks held, but also on the loans in their portfolio

ANSWER
Answer: D