Why does it become difficult to read old fossils?
a. older fossils are difficult to obtain because they’re extremely deep in the earth’s crust.
b. older fossils are biologically less important than newer ones.
c. older fossils provide less information about evolution.
d. older fossils are only formed by sedimentation.

What best describes the dropping height of a ball that bounces back up to a height of 45 cm

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?

Pulmonary arteries carry highly oxygenated blood. true or false?