Final answer:
A CD4+ cell count of less than 200 cells/µL meets the CDC case definition for a diagnosis of AIDS.
Step-by-step explanation:
According to the CDC classification system, the CD4+ cell count that meets the case definition for a diagnosis of AIDS is (A) Less than 200 cells/µL. A healthy person typically has about 1,000 CD4+ T cells per microliter of blood. When the CD4+ T cell count falls below 200 cells/µL, the individual's immune system is severely compromised, and they can be formally diagnosed with AIDS. This condition makes them more susceptible to opportunistic infections and is a critical threshold in the progression of HIV to AIDS. In a clinical setting, the monitoring of CD4+ T cell counts is essential for adjusting treatment to prevent the decline in the immune function.