## Core Concept
Light's criteria are used to differentiate between **exudative** and **transudative** pleural effusions. These criteria help in determining the cause of pleural effusion by analyzing the characteristics of the pleural fluid.

## Why the Correct Answer is Right
The correct answer is related to the specifics of Light's criteria, which include:
- The ratio of pleural fluid protein to serum protein greater than 0.5
- The ratio of pleural fluid lactate dehydrogenase (LDH) to serum LDH greater than 0.9
- Pleural fluid LDH greater than two-thirds the upper limit of the laboratory's serum LDH reference range

## Why Each Wrong Option is Incorrect
- **Option A:** This option is not provided, but typically, correct statements about Light's criteria would include the protein and LDH ratios and the absolute value of LDH in pleural fluid.
- **Option B:** Similarly, without content, we assume any accurate description of Light's criteria would be correct.
- **Option D:** Again, without specifics, any statement aligning with established Light's criteria would be a correct assertion.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that **Light's criteria are sensitive but not specific** for identifying exudates. This means while they can help identify most exudative effusions, they might misclassify some transudates (e.g., in heart failure with high diuretic doses) as exudates.

## Correct Answer: D.