First one who answers this correctly will be marked brainliest, , and 5 stars will be given!

what is ridge push?

a) cooler, denser crust sinks into the mantle

b) when edges become denser and gravity pulls them downward and away from one another

c) currents just beneath earth’s crust flow very slowly, causing movement in the plates above them

d) folding and crumpling and sliding upward creating mountains

Astudy by solloch and et. al., in 2017, gives the map above which shows the frequency of alleles with a ccr5-delta32 mutations over 87 different countries. this mutation deletes the presence of a co-receptor (ccr5) on the outside of human t-cells (lymphocytes). some viruses, such as the one responsible for the black death and human immunodeficiency virus (hiv), require this receptor for attachment to host cells during the infection process. the black death was an epidemic that passed over northern europe during the 14th century killing nearly 60% of europeans. according to this information, which explanation best explains why northern europeans show a greater immunity for hiv than some other parts of the world?