In the deep waters of the ocean, coral reefs are found in abundance. Algae live within these coral reefs, producing pigments that give corals their color and providing nutrients that corals need to survive. In return, corals offer shelter to the algae. So, coral and algae share a association. Climate change has led to increasing ocean temperatures, which can cause corals to expel the algae living inside of them. This phenomenon is known as coral bleaching because it causes corals to lose the pigments produced by the algae. Coral bleaching will lead to What kind of game was Pole Position?

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?