Roman money began to lose its value when
a.
the government circulated less money
b.
less silver was used in coins
c.
persian gold replaced roman coins
d.
emperors kept changing currency

B.  less silver was used in coins

Explanation:

Due to the need to produce more light weight coins, the silver quantity in most roman coins were reduced until the coins lost their value. This also heralded the emergence of counterfeit coins into the market.