An advantage of light microscopes compared to electron microscopes is that light microscopes?
a. allow you to view the surface of cells in greater detail than electron microscopes
b. have a higher magnification capability because they use natural light
c. allow you to to view living cells, while electron microscopes do not
d. have a greater resolution available because they use white light

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?