A．Niche phone cards.
B．International phone cards.
C．Domestic phone cards.
D．Prepaid phone cards．

A．Commercial product taxes．
B．Connection fees．
C．Pay phone charges.
D．Initial fees.

A．Cards with the least additional fees．
B．Cards with a low rate and other fees．
C．Cards with no maintenance fees.
D．Cards with a high rate and low service fees.