How do the human nervous system and endocrine system interact in response to a stimulus?
O
A. The endocrine system signals the nervous system to send out
nerve impulses in response to a stimulus.
B. The nervous system signals the endocrine system to release
hormones in response to a stimulus.
C. The nervous system responds to a stimulus, and the endocrine
system returns the body to a relaxed state.
D. The endocrine system responds to a stimulus, and the nervous
system returns the body to a relaxed state.

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?