A large volcanic eruption can change features of Earth and destroy many populations at once.
Which statement describes a possible benefit of such an eruption?
O A. Volcanic ash falls to the ground and adds minerals to the soil,
making it rich for plant growth.
B. Lava flowing from the volcano covers the soil, making it unusable
for living things that grow in it.
C. The air is filled with ash, making it hard for animals to breathe.
D. Clouds of ash block sunlight, making it impossible for plants to
carry out photosynthesis.

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?