This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Basic Concepts and Vascular changes of Acute Inflammation, Subject name: Pathology
A 36-year-old woman with pneumococcal pneumonia develops a right pleural effusion. The pleural fluid displays a high specific gravity and contains large numbers of polymorphonuclear (PMN) leukocytes. Which of the following best characterizes this pleural effusion? 
Select and explain. 
A. Fibrinous exudate, B. Lymphedema, C. Purulent exudate, D. Serosanguineous exudate
C: Purulent exudate
Answer: C: Purulent exudate 
Explanation: -The pleural effusion encountered in this patient represents excess fluid in a body cavity. Transudate-Edema fluid with low protein content Exudate-Edema fluid with high protein content. Purulent exudate or effusion contains a prominent cellular component (PMNs). Serous exudate or effusion is characterized by the absence of a prominent cellular response and has a yellow, straw like color. Fibrinous exudate (choice A) does not contain leukocytes. Serosanguineous exudate (choice D) contains RBCs and has a red tinge. Diagnosis: Bacterial pneumonia, pleural effusion