The human immunodeficiency virus (HIV) infects and kills cells of the immune system. A person infected with HIV can be treated with the antiviral medication AZT. This medication slows the progression of HIV by preventing the virus from integrating into the individual's genome. What is the best explanation of why AZT slows the progression of HIV?

Explanation:

AZT known as Zidovudine is an antiretroviral drug, and used in the treatment of human immunodeficiency virus (HIV) infection called AIDS. As it is a  nucleoside reverse transcriptase inhibitor, it slows the progress of HIV infection by inhibiting replication of HIV by RT, and it's main target is reverse transcriptase enzyme.  

HIV destroys cells, called CD4 T cells (T helper cells). These cells are very important cells of our immune system.

AZT slows down the progress of HIV infection by decreasing virus load in the body.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.