Do all mammals have 4 true or false? ?

Which mantle is under the crust the upper mantle or the lower mantle i think it's upper let me know if i'm right

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.

Indica el nombre y la fucion de los vasos sanguineos que entran y salen de los riñones