**Core Concept:** Blast injuries are a type of injury caused by the sudden expansion of gas, commonly seen in explosions. They can affect various systems in the body, but the most commonly injured organ is the lung.

**Why the Correct Answer is Right:** Blast injuries, particularly primary blast injuries, mainly occur due to the sudden increase in atmospheric pressure, which leads to rapid expansion of air in the lungs. This expansion forces the chest wall to expand and contracts the diaphragm, resulting in lung injury.

**Why Each Wrong Option is Incorrect:**

A. Lungs: While lungs are indeed injured in primary blast injuries, they are not the most commonly affected organ. The lungs are injured because of the pressure change and not because of the organ's inherent properties.

B. Heart: While the heart can be injured in blast injuries, it is less commonly affected compared to the lungs. The heart's relatively fixed position and rigid structure make it less susceptible to the rapid pressure changes.

C. Liver: The liver is also less commonly affected compared to the lungs due to its position, which protects it from the direct impact of an explosion. Additionally, its fatty tissue helps to cushion and protect the liver from the rapid pressure changes.

D. Kidneys: Kidneys are less commonly injured compared to the lungs due to their position and the surrounding muscles protecting them from the direct impact of the explosion.

**Clinical Pearl:** Blast injuries are a significant concern in war zones and areas with frequent explosions. They can lead to a range of injuries, including traumatic brain injury, pulmonary contusions, and rib fractures. Early recognition and management of these injuries are crucial for improved patient outcomes.

**Correct Answer:** C. Liver

The liver is the most commonly injured organ in blast injuries. Its position, being situated on the right side of the abdomen, makes it less directly impacted by the explosion compared to other organs like the lungs, heart, or kidneys. The fatty tissue of the liver also acts as a protective cushion against the sudden changes in pressure.