The answer is c-Ziehl Nelsen stain. 

Ziehl Nelsen stain is a special stain used for the detection of acid-fast bacteria such as Mycobacterium tuberculosis. This stain is not routinely used for the direct smears of pleural and peritoneal fluid, as acid-fast bacteria are not commonly found in these fluids. 

Gram stain, on the other hand, is routinely used for the direct smears of pleural and peritoneal fluid, as it helps to identify the presence of bacteria and their morphology. Eosin-nigrosin stain and Leishman stain are also commonly used for the direct smears of these fluids to identify various types of cells present in the fluid.

References:
1. Forbes BA, Sahm DF, Weissfeld AS. Bailey & Scott's Diagnostic Microbiology. 12th ed. St. Louis, MO: Mosby Elsevier; 2007.
2. Mackie and McCartney Practical Medical Microbiology. 14th ed. Churchill Livingstone; 1996.