Edward Jenner discovered vaccinations. He found that some of the dairymaids who worked with cows had suffered lesions on their hands, and that these dairymaids were immune to the more severe smallpox. Which best explains why the dairymaids were immune to smallpox?
They did not interact with many people so they were not exposed to the pathogen.
They frequently washed their hands so they were able to wash away the pathogen.
They were exposed to cowpox, and the substance their body produced to fight cowpox also attacked smallpox.
They breathed the air around the cows that carried an antipathogen in it that destroyed the pathogen.

Agenus is a taxonomic grouping that identifies a collection of species. when a scientist discovers a new species, how is this species assigned to a genus

Explain the process that creates the heat of the sun?

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?