Using birth control entirely eliminates the risk of having a unplanned pregancy

False.

Using birth control may be affective for whom are in there twenties or older because, there bodies have already fully developed and the have a normal cycle.

Teen's that use birth control have a higher chance of getting pregnant because, there bodies aren't mature or is there cycle.  This is why it's false.

In many cases females become pregnant even when on birth control, birth control can't prevent pregancy most of the time. It's not rare for a feamle on birth control to get pregnant.

c would be the answer