**Question:** Intralobar sequestration of lung is commonest in the -

**Core Concept:**
Intralobar pulmonary sequestration is a congenital anomaly where an area of lung tissue is separated from the normal bronchopulmonary circulation and receives blood supply from an aberrant systemic artery. This results in an ischaemic, non-functional area of lung tissue.

**Why the Correct Answer is Right:**
The correct answer is **D** because intralobar sequestration is a type of pulmonary sequestration, where the affected lung tissue is attached to the main bronchus of a lobe within the lung. In contrast, extralobar sequestration is a type of pulmonary sequestration where the affected lung tissue is not attached to the main bronchus but is supplied by a systemic artery.

**Why Each Wrong Option is Incorrect:**

A. **False:** Extralobar sequestration is the less common type of pulmonary sequestration, not intralobar sequestration.

B. **False:** This option does not address the concept of pulmonary sequestration and its relation to the main bronchus.

C. **False:** Intralobar sequestration is not specific to the right lower lobe, as it can occur in any lobe.

D. **Correct:** As mentioned earlier, intralobar sequestration is a type of pulmonary sequestration where the affected lung tissue is attached to the main bronchus of a lobe within the lung. This makes option D the correct answer.

**Clinical Pearl:**
Pulmonary sequestration is a rare congenital anomaly that can be classified as intralobar or extralobar based on its relation to the main bronchus and systemic arterial supply. It is important for clinicians to understand the distinction between these two types to make accurate diagnoses and provide appropriate treatment options for patients with respiratory symptoms due to pulmonary sequestration.

**Correct Answer:** D. Intralobar sequestration.