Which one of the following is employed as antihistamine?

An antihistamine is a type of pharmaceutical drug that opposes the activity of histamine receptors in the body. Diphenyl hydramine is employed as an antihistamine. Here, omeprazole is used in the treatment of peptic ulcer diseases. Chloramphenicol is an antibiotic and Norethindrone is an antifertility drug. Hence, option C is correct.