A prothallium, or prothallus<span> is usually the </span>gametophyte<span> stage in the life of a </span>fern<span> or other pteridophyte. Occasionally the term is also used to describe the young </span>gametophyte<span> of a liverwort or peat moss as well.</span>
The term being describe above is the hormonal method in which it prevents the egg from reaching the ovaries to prevent the women from being pregnant during intercourse. There are different types of hormonal methods being used, and it does not only prevent eggs in reaching ovaries but it prevents also sperm in reaching the uterus.
The name of the locatuon is called an active site.
D all of these create a magnetic field. let me know if you want me to explain.