An unlabeled hierarchical diagram of some astronomical bodies is shown. The labels A, B, C, and D can be used to represent galaxies, solar system, clusters, universe, and planets.

An image of four circles nestled one within the other is shown. The lower boundary of all four circles touch one another. The largest and the outermost circle is labeled A. The next circle in order is labeled B. The next circle is labeled C. The innermost circle is labeled D.

Part 1: Which four astronomical bodies would you choose to represent the four labels in the diagram?
Part 2: Justify your choice based on the hierarchical relationships in astronomical bodies.

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?