**Core Concept**
Shock lung, also known as acute respiratory distress syndrome (ARDS), is a condition where the lungs become damaged due to inflammation and fluid accumulation, leading to impaired gas exchange and respiratory failure. This condition is often a complication of severe trauma, sepsis, or shock. The pathophysiology involves disruption of the alveolar-capillary membrane, resulting in increased permeability and fluid leakage into the alveoli.

**Why the Correct Answer is Right**
The correct answer is related to the pathophysiological changes that occur in shock lung. The hallmark of ARDS is the presence of bilateral lung infiltrates on chest radiography, which is indicative of fluid accumulation in the alveoli. The condition is characterized by a non-cardiogenic pulmonary edema, which is not responsive to fluid challenge. The inflammatory response and release of pro-inflammatory cytokines play a crucial role in the development of ARDS.

**Why Each Wrong Option is Incorrect**
**Option A:**
This option is incorrect because shock lung is not primarily characterized by an increase in pulmonary vascular resistance. While pulmonary hypertension can occur in ARDS, it is not a defining feature of the condition.

**Option B:**
This option is incorrect because shock lung is not primarily characterized by an increase in cardiac output. While cardiac dysfunction can contribute to the development of ARDS, it is not a primary feature of the condition.

**Option C:**
This option is incorrect because shock lung is not primarily characterized by an increase in respiratory rate. While tachypnea can occur in ARDS, it is not a defining feature of the condition.

**Clinical Pearl / High-Yield Fact**
A key clinical feature of shock lung is the presence of a normal or low cardiac output in the setting of hypoxemia. This is often referred to as a "normal" or "low" cardiac index, despite the presence of significant respiratory distress.

**Correct Answer: B. Non-cardiogenic pulmonary edema.**