**Core Concept**
TB (tuberculosis) is a bacterial infection caused by Mycobacterium tuberculosis, which primarily affects the lungs but can also involve other parts of the body. The spread of TB to extrapulmonary sites occurs through hematogenous dissemination or direct extension from the primary site.

**Why the Correct Answer is Right**
Lymph nodes are the most common site of extrapulmonary TB due to their role in filtering blood and lymph fluid. When TB bacteria enter the bloodstream, they are often filtered out by the lymph nodes, leading to their involvement. This can occur in various regions, including the cervical, axillary, or abdominal lymph nodes. The involvement of lymph nodes in TB is often associated with a worse prognosis and more severe disease.

**Why Each Wrong Option is Incorrect**
**Option A:** Bone TB is a well-known complication of TB, particularly in immunocompromised patients or those with poor nutrition. However, it is not the most common site of extrapulmonary TB.
**Option C:** Pleural TB is a form of extrapulmonary TB that affects the pleura, the lining surrounding the lungs. While it is a significant complication, it is not the most common site of extrapulmonary TB.
**Option D:** Ileocecal TB is a type of extraintestinal TB that affects the ileocecal region of the small intestine. Although it is a common site of extraintestinal TB, it is not the most common site of extrapulmonary TB overall.

**Clinical Pearl / High-Yield Fact**
The "Rule of 3" in TB states that if a patient has TB for more than 3 months, has a positive sputum smear, or has extrapulmonary TB, they are more likely to have a poor prognosis and a higher likelihood of transmission to others.

**✓ Correct Answer: B. Lymph nodes**