General Medicine General c2ad0180 A 40 year old male repoed with recurrent episodes of oral ulcers, large areas of denuded skin and flacid vesiculo-bullous eruptions. Which is the most impoant bed-side investigation helpful in establishing the diagnosis - A Gram staining of the blister fluid B Culture and sensitivity C Skin biopsy and immunoflurescence D Tzanck smear from the floor of bulla