Answer:
Adoption studies compare the similarity between an adoptee and his or her biological versus adoptive relatives, or the similarity between biological relatives of affected adoptees with those of unaffected or control adoptees. The latter approach is more powerful because it eliminates the potentially confounding effect of environmental factors.
Explanation:
the skeleton has been considered
I think the answer is radiation.
hope it helps
Viruses are the microorganisms who needs to infect the living host cells, in order to replicate or reproduce. These infectious agents are capable of injecting and infecting all the life forms present, including the plants, animals and bacteria. The viruses were not among the first organisms to evolve as in order to replicate themselves and continue through the time they needed other organisms' cell.
Hence, the correct answer is 'viruses have to infect a living cell in order to reproduce'.
I think the correct answer is the first option. The key features of chordates would be notochord, dorsal tubular nerve cord, pharyngeal pouches, and a tail. These features appears in some period of their lives. They are deutorostomes where the anus would be formed first before the mouth.