Final answer:
The nurse should withhold the next dose of heparin.
Step-by-step explanation:
Option C, withhold the next dose of heparin, is the correct action for the nurse to take when a client on heparin therapy presents with hematuria and a prolonged partial thromboplastin time (PTT) of 96 seconds. Hematuria, or blood in the urine, is an adverse reaction associated with heparin therapy, and a prolonged PTT indicates that the client is at risk for bleeding. Withholding the next dose of heparin helps prevent further bleeding complications.