**Core Concept:**
Congenital Tuberculosis (TB) is a rare but severe form of the disease caused by the Mycobacterium tuberculosis bacillus, which primarily affects infants and children. It occurs when an infected mother passes the bacteria to her newborn child during pregnancy, childbirth, or breastfeeding.

**Why the Correct Answer is Right:**
Congenital TB primarily affects infants and children because the immune system of newborns is immature, making them more susceptible to the disease. In this case, the most common organ involved is the **Lungs**. TB affects the lungs because the respiratory system is the primary entry point for the bacteria, and the lungs have a high blood supply that facilitates the spread of the infection throughout the body.

**Why Each Wrong Option is Incorrect:**
A. **Bones and Joints (Vertebrae)** - TB can involve bones and joints, but this is a rare presentation of the disease, not the most common organ.
B. **Central Nervous System (CNS)** - Although TB can affect the CNS, it is less common than pulmonary involvement.
C. **Heart and Kidneys** - TB affecting the heart and kidneys is also possible, but less common than lung involvement.
D. **Gastrointestinal system** - TB affecting the gastrointestinal system is uncommon, as the bacteria primarily target the lungs.

**Clinical Pearl:**
The most common organ affected by congenital TB is the lungs. This emphasizes the importance of early diagnosis and treatment to prevent severe complications and ensure better outcomes for infants and children.

**Correct Answer:** **Lungs**