In 1863 the United States government began providing which of the following to mail carriers

A．It was very easy to counterfeit.
B．It increased the cost of mail delivery.
C．It was difficult to affix to letters.
D．It had to be purchased by the sender in advance.

A．at a community college within his own state
B．at a public university
C．within his own state
D．at a four-year college