Pls help im having issues and idk what the answer is! ill give brainliest!!

The gene that causes sickle-cell disease is present in a higher percentage of residents of sub-saharan africa than among those of african descent living in the united states. even though this gene causes sickle-cell disease, it also provides some protection from malaria, a serious disease that is widespread in sub-saharan africa but absent in the united states. discuss an evolutionary process that could account for the different percentages of the sickle-cell gene among residents of the two regions.

Which part of cellular respiration must occur before any of the other steps can occur

Plz ! ive been stuck on this forever