The only disease out of these that is caused by a prion is mad cow disease, and is therefore the correct answer. HIV is caused by a virus, syphilis and tuberculosis by bacteria, and lupus is an autoimmune disorder.

Reverse transcriptase is the epitome of viral evolution, as showcased by the HIV virus. Reverse transcriptase enables the HIV virus to create a DNA template from an RNA segment already encapsulated in the virus, but using the host cell's own DNA replication machinery.

When you think of viruses, think of them as parasites: they prey on host cells and take advantage of their resources. Viruses require the reproductive machinery of host cells in order to reproduce and use the energy in the cells to drive the synthesis processes; however, it is possible for viruses to remain virulent outside of a host for long periods of time. When not infecting a host, viruses are refrred to as virions. Essentially, viruses can survive outside of a host, but cannot replicate.

At no point in the reproductive cycle of a virus does it contain ribosomes. Instead, it uses the ribosomes found in the host cell to synthesize the proteins needed for its reproduction.

Influenza mutates rapidly, and can mutate into a new virus and evade previous vaccines. As a result, new vaccines must be created in order to provide the best defense against the influenza virus for that year. The vaccine you get one year is not going to be the same vaccine you get the next year.

Vaccines allow the body to produce antibodies to the exposed pathogen. They do not provide antibodies.

Because the question refers to a bacteriophage, we know that the two answers beginning with endocytosis are incorrect; endocytosis begins the multiplication cycle of an enveloped virus. Bacteriophages are naked viruses, contained within a protein capsule with no outer membrane.

During adsorption, the virus encounters a susceptible bacterial host cell and adsorbs (binds) to receptor sites on the cell membrane like a key fitting into a lock. The flexible cell membrane of the host cell is then penetrated by the viral nucleic acids. During synthesis, the viral nucleic acids take control over the host’s metabolic processes, much like the machinery of a factory assembly line. This causes the host cell to replicate and assemble new viral particles. Once the new viruses are assembled, the host cell ruptures (lyses) and the viruses are released to find new host cells. 

The non-specific host response includes fever, inflammation, positive chemotaxis, and phagocytosis. These responses are directed at any perceived invader, and therefore are non-specific.

The specific host response targets a specific invader, and includes T-cells, B-cells, and antibodies.

Eukaryotic cells have a nuclei; prokaryotic cells have no nuclei.

Eukaryotic cells are considerably larger and more complex. Eukaryotic cells possess membrane-bound organelles; prokaryotic cells, which are smaller and less complex, do not. Both eukaryotic and prokaryotic cells can have flagella, but not necessarily in all cases.

Note that ribosomes are not membrane-bound, and are found in both prokaryotes and eukaryotes.

Some viruses have a DNA genome, while others use RNA. While DNA may be a crucial component to determining life, it cannot be used to differentiate viruses from living organisms because some viruses do carry their own DNA.

All viruses can be differentiated from living organisms because they do not "eat" or absorb nutrients, they do not have cells, they do not respond to stimuli, and they do not reproduce independently. All living organisms absorb nutrients, have cells, respond to stimuli, and are capable of reproduction, thus making viruses different.

Lysosomes are structures within cells which contain digestive enzymes to eliminate waste and debris.

Neutrophils are the most abundant of the leukocytes making up 40-70% of white blood cells.

Basophils are the least common, representing only about 0.5% of all white blood cells.

Natural killer (NK) cells are lymphocytes, not leukocytes. They compose a small fraction of lymphocytes within the innate immune system.