One Potential Problem with Having Private Currencies-Such as "Bank of Sam

One potential problem with having private currencies-such as "Bank of Sam" dollars and "Bank of Fred" dollars-is that it will be difficult for individuals to

A) compare Sam dollars to Fred dollars.
B) trade Sam dollars for Fred dollars.
C) discourage both Sam and Fred from inflating their currencies.
D) keep both Sam dollars and Fred dollars in their wallets.