Which compounds most likely has atoms held together by covelent bonds

Y’all i need answers plss people are saying me and my brother look alike although we’re two different ages. one year apart i’m a girl, btw i’m thinking we could be fraternal twins idk my parents and my friends think we look alike

The breakdown of food is accomplished by enzymes. a. physical b. chemical c. mechanical d. none of the above

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?