Ohhh goddd are you serious
100% method is only one! don't make a sex!
All another method have some <span>possibility (</span>chance)
Approximately 50 Percent of the people in the United States who die, do so because of what they do
Quantitative research<span> is a formal, objective, systematic process in which numerical data are used to obtain information about the world. This </span>research<span>method is used: to describe variables; to examine relationships among variables; to determine cause-and-effect interactions between variables.</span>
Some of the reasons can be:
If you're a pre-teen or a teenager who has only started menstruating, you may find that it takes a while for your period to settle in and become regular.
I couldn't think of anything else, but hope this helped enough!
To find the best answer, ask your mom!
~Aurora