This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Medicine
Which one of the following parameter is consistent with pleural transudate? 
Select and explain. 
A. Ldh<2/3 of upper limit of serum ldh, B. WBC -1500/mm3, C. Specific gravity-1.120, D. Protein-2.5gram/dl
A: Ldh<2/3 of upper limit of serum ldh
Answer: A: Ldh<2/3 of upper limit of serum ldh 
Explanation: Pleural fluid LDH levels greater than 1000 IU/L suggest empyema, malignant effusion, rheumatoid effusion, or pleural paragonimiasis. The diagnosis is suggested by a pleural fluid/serum LDH ratio of greater than 1, with a pleural fluid/serum protein ratio of less than 0.5 Normal levels of LDH in the blood can vary depending on the lab, but usually range between 140 units per liter (U/L) to 280 U/L for adults and tend to be higher for children and teens Ref Davidson edition23rd pg 626