What are the characteristics of convertible and inconvertible paper money?
a. Convertible paper money is backed by gold and silver, while inconvertible paper money is not.
b. Convertible paper money can be exchanged for metal currency at any time, while inconvertible paper money cannot.
c. Convertible paper money is of legal acceptance but not of forced acceptance, while inconvertible paper money is of forced acceptance.
d. Convertible paper money is issued by the state, while inconvertible paper money is issued by banks.

a) b and c are correct.
b) a and d are correct.
c) b and d are correct.
d) a and c are correct.