B is the correct answer. They can sometimes show an extinction but not always.
Answer:
A period happens because of changes in hormones in the frame. Hormones are chemical messengers. The ovaries launch the lady hormones estrogen and progesterone . those hormones motive the liner of the uterus (or womb) to build up. The constructed-up lining is prepared for a fertilized egg to connect to and begin developing. If there is no fertilized egg, the liner breaks down and bleeds. Then the identical manner occurs all once more.
It normally takes about a month for the liner to build up, then smash down. this is why a lot of ladies and women get their periods round once a month.
Source:
https://kidshealth.org/en/teens/menstruation.html
https://www.plannedparenthood.org/learn/health-and-wellness/menstruation
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natural selection light water and carbon dioxide
<span>This research study would be a prospective cohort study. </span>
<span>In this study, the groups are different in some way, for example, a control group which received no treatment, a standard group who received a well-studied drug and a test group who received a new drug. These groups are followed over time and the outcome (such as curing a disease or alleviating symptoms) will be compared. </span>
