Two weeks in a row are rainy, cancelling Lizette's weeding sessions. When she gets back out to the garden, the weeds are huge. Lizette peeks under the leaves of the weeds and observes some struggling radishes and carrots. They are small and yellowish and look unhealthy.
Since it has rained for two weeks, she knows the plants have plenty of water. Which of the following must also be present for the vegetables to grow
and thrive?
A food
B butterthes
C DNA
D cells be

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?