**Core Concept**
Chronic passive congestion of the lungs is a condition characterized by the accumulation of fluid in the lung tissue due to impaired lymphatic drainage or increased pressure in the pulmonary veins. This can lead to pulmonary edema and compromised gas exchange.

**Why the Correct Answer is Right**
Chronic passive congestion is often secondary to left-sided heart failure, particularly left ventricular failure. The increased pressure in the left atrium and pulmonary veins impairs lymphatic drainage, leading to fluid accumulation in the lung interstitium. This is due to the backpressure in the pulmonary veins causing fluid to leak out into the lung tissue.

**Why Each Wrong Option is Incorrect**
* **Option A:** Right-sided heart failure typically leads to cor pulmonale, which is characterized by increased pressure in the pulmonary arteries rather than the pulmonary veins.
* **Option B:** Chronic obstructive pulmonary disease (COPD) can lead to pulmonary congestion due to increased pressure in the pulmonary arteries, but it is not typically described as "passive congestion."
* **Option D:** Pulmonary embolism can cause acute pulmonary edema, but it is not typically described as "chronic passive congestion."

**Clinical Pearl / High-Yield Fact**
Chronic passive congestion is a classic sign of left-sided heart failure, and it is often associated with a plethoric (engorged) liver due to the increased pressure in the hepatic veins.

**Correct Answer: C. Left ventricular failure.**