In a few sentences, explain what hiv and aids are and how hiv is spread.

HIV attacks and destroys the immune system's infection-fighting cells, called CD4 cells. They also are called CD4 positive T cells. HIV gets into these cells, makes copies of itself, and kills the healthy cells. As a person loses CD4 cells, the immune system weakens, making it harder for the body to fight infections and cancer. There are many different strains (types) of HIV. Most people have the HIV-1 strain. But, a person can be infected with more than one strain at a time.

Difference between normal and abnormal tissue is much clearer on mri than on ct and mri much suitable to view soft tissues

Answer (185 billion dollars).