Parasite and Host, because the tapeworm can not live without the cells of the Human Intestine. It needs to live off of the Human making it, the host for the tapeworm.
Answer by Mimiwhatsup: A one step process where one atom of helium is generated from four atoms of hydrogen.
Why: "Hydrogen fusion (nuclear fusion of four protons to form a helium-4 nucleus) is the dominant process that generates energy in the cores of main-sequence stars. It is also called "hydrogen burning", which should not be confused with the chemical combustion of hydrogen in an oxidizing atmosphere." (Wikipedia)
I think it’s secondary mutations at least and it must be