A bird flew and landed on its swing. When the bird "hit" the swing, the swing began to move back and forth. What happened when the bird landed on the swing?

A. Energy was transferred from the air to the swing.
B. The swing and the bird gained energy.
C. The swing's energy and the bird's energy each stayed the same.
D. Some of the bird's energy was transferred to the swing.

Which nucleotide component contains nitrogen

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?

Need asap plz hurry im being timed when a body cell divides through the process of mitosis, the chromosomes in the daughter cells a. represent only the healthiest chromosomes from the parent cell. b. represent only half of the chromosomes in the parent cell. c. are identical to the chromosomes of the parent cell. d. are formed when chromosomes from the parent cell cross over.