Finish the following sentence with the best choice: How do I keep track of my menstruation?

Choices:
- Keep a small spoon and a red pen in your nightstand, when your period starts, mark the spoon with a red x on the days you menstruate, that way you can tell how long it is from one period to another.
- Keep a small calendar and a red pen in your nightstand, when your period starts, mark the calendar with a red x on the days you menstruate, that way you can tell how long it is from one period to another.

Answer:
Keep a small calendar and a red pen in your nightstand, when your period starts, mark the calendar with a red x on the days you menstruate, that way you can tell how long it is from one period to another.