**Core Concept**
Acute Respiratory Distress Syndrome (ARDS) is a life-threatening condition characterized by rapid onset of non-cardiogenic pulmonary edema, leading to hypoxemic respiratory failure. It is often caused by direct lung injury, such as pneumonia or aspiration, or indirect lung injury, such as sepsis or trauma.

**Why the Correct Answer is Right**
ARDS is characterized by inflammation, increased permeability of the alveolar-capillary membrane, and impaired gas exchange. The pathophysiology involves the release of pro-inflammatory cytokines, such as TNF-alpha and IL-1 beta, which lead to the activation of endothelial cells and the release of von Willebrand factor, causing platelet aggregation and microthrombi formation. This results in increased permeability and fluid leakage into the alveoli, leading to hypoxemia.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because hypercapnia is not a characteristic feature of ARDS. In fact, patients with ARDS often have a normal or decreased PaCO2 level due to hyperventilation.
**Option B:** This option is incorrect because bilateral lung infiltrates on chest radiograph are a characteristic feature of ARDS, not a distinguishing feature.
**Option C:** This option is incorrect because pulmonary artery pressure is often normal or decreased in ARDS, as the condition is characterized by non-cardiogenic pulmonary edema.

**Clinical Pearl / High-Yield Fact**
A key feature of ARDS is the lack of response to positive end-expiratory pressure (PEEP) in the first 24-48 hours, which distinguishes it from cardiogenic pulmonary edema.

**Correct Answer: C.**