In which of the following cases should a nurse hold the prescribed medication and question the order?

A. A client with heart rate of 50 and blood pressure of 88/52 mm Hg who has an order for intravenous nitroglycerin.
B. A client who is eight weeks' gestation with a new prescription for isotretinoin for acne.
C. A client who is on an IV heparin infusion with a platelet count of 167,000 cells/mmA3.
D. A client with a mechanical heart valve and INR 1.8 who has an order for warfarin five milligrams.
E. A client with a penicillin allergy who has an order for trimethoprim-sulfamethoxazole