How does natural selection produce change? Help please

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?

Brian made this table to organize his notes on changes of state change of state energy change melting gain freezing lose deposition gain condensation lose

The source of energy shown in the image is (renewable, non renewable, polluting) a drawback of building a dam is that (it will destroy ecosystems, it requires fossil fuels, it won’t be useful for irrigation)