The answer is c-Ziehl Nelsen stain.

Direct smears of pleural and peritoneal fluid are routinely stained with Gram stain and Leishman stain to identify bacterial and fungal infections, respectively. Eosin-nigrosin stain is used for the detection of fungi and parasites in clinical specimens. However, Ziehl Nelsen stain is not routinely used for pleural and peritoneal fluid smears because it is primarily used for the detection of acid-fast bacilli, such as Mycobacterium tuberculosis, which are not commonly found in these fluids.

According to a study published in the Journal of Clinical Microbiology, Ziehl Nelsen staining of pleural fluid smears has a low sensitivity and specificity for the diagnosis of tuberculosis compared to culture and PCR methods (https://jcm.asm.org/content/45/12/4061). Therefore, it is not recommended as a routine staining method for pleural and peritoneal fluid smears.

In summary, direct smears of pleural and peritoneal fluid are routinely stained with Gram stain and Leishman stain, but not with Ziehl Nelsen stain, due to its limited usefulness for the detection of acid-fast bacilli in these fluids.