**Core Concept**
AIDS-defining conditions are clinical manifestations that indicate the progression of HIV infection to Acquired Immunodeficiency Syndrome (AIDS). These conditions result from the severe immune suppression caused by HIV, leading to opportunistic infections or malignancies.

**Why the Correct Answer is Right**
The correct answer is **Pulmonary tuberculosis (TB)**, as it is a condition that can be caused by HIV, but it is not exclusive to AIDS. HIV-infected individuals are at increased risk of developing TB, but pulmonary TB can also occur in individuals without HIV. The immune suppression in HIV-infected individuals makes them more susceptible to TB, but it is not a defining condition of AIDS.

**Why Each Wrong Option is Incorrect**
**Option A:** Toxoplasmosis is a CNS infection caused by the protozoan Toxoplasma gondii, which is a common AIDS-defining condition. It occurs when the immune system is severely compromised, allowing the parasite to reactivate.
**Option B:** Cryptococcal meningitis is a fungal infection caused by Cryptococcus neoformans, which is a classic AIDS-defining condition. It occurs when the immune system is severely compromised, allowing the fungus to cause meningitis.
**Option C:** Kaposi's sarcoma is a type of cancer that is strongly associated with HIV infection and is considered an AIDS-defining condition.

**Clinical Pearl / High-Yield Fact**
AIDS-defining conditions are clinical manifestations that indicate the progression of HIV infection to AIDS, and they are often opportunistic infections or malignancies that occur in individuals with severe immune suppression.

**Correct Answer:** D. Pulmonary tuberculosis (TB)