Plant cells have what is perhaps the most complex outer coverings. Plant cell walls are made largely of cellulose which forms strong, highly rigid, almost indigestible coverings that protect the cell and gives it shape.
Answer:The rock formations of eastern North America, Western Europe, and northwestern Africa were later found to have a common origin, and they overlapped in time with the presence of Gondwanaland. Together, these discoveries supported the existence of Pangea.When Rodinia broke up, it split into three pieces: the supercontinent of Proto-Laurasia, the supercontinent of Proto-Gondwana, and the smaller Congo craton. Proto-Laurasia and Proto-Gondwana were separated by the Proto-Tethys Ocean.
Don't take my full word on it, this is what i think
Explanation:
Hydrogen because it only has one valence electron I believe.
Your answer is going to be A. Excretory.