Read the information below. Then use it to answer the following question. A car’s tires feel a lot of force when they pass over holes or bumps in a road. Shock absorbers help dull the force coming from the road so that a vehicle shakes less in response. This makes the ride for passengers within the car smoother and more pleasant.

The analogy below compares the relationship between pH and specialized chemicals. Choose the answer that best completes this analogy.

_[blank]_ : solution pH :: shock absorbers : vehicle movement

Explain how sequences of amino acids in proteins can be used to reveal relationships among organisms.

What is responsible for the uneven heating between the poles and the equator on any given day

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?