This is a test of commonsense with single/multi-choices. Complete the next sentence:

How to know if menstrual periods have stopped
Evaluate the contraceptives you're taking.
If you missed a period while on birth control pills, your period may be irregular or absent longterm depending on how you use the medication and your body's reaction to it.
Oral contraceptives typically come in 21 day packs with 7 days worth of inactive placebo pills.

Pick your answer from:
(a). Expect menstrual periods to last between 30 and 90 days. While they're not foolproof, you may still notice changes after they have stopped.
(b). While taking these pills, you should have your period. If you skip the placebo pills and go straight into the next pack, you will probably miss your period.
(c). Penile prolapse may interfere with the process of getting pregnant for some women. ( but it is a relatively universal problem.
(d). These include some containing other active post-menstrual hormones that help many women get pregnant. Ask your doctor about the due date.
The answer is:
(b).