Mariah Is Getting Used to Having a Cell Phone

Mariah is getting used to having a cell phone. This first month she was surprised by several extra charges on her bill, and called her cell phone service provider.
-On the bright side, the agent explained to Mariah that since this was her first month that she did not have any ____ minutes. But in the future, this type of unused minutes could be applied to the next month's bill.

A) roaming
B) rollover
C) anytime
D) in network