【单选题】

The nurse is administering warfarinCoumadin) to a client with deep vein thrombophlebitis. Which laboratory value indicates warfarin is at therapeutic levels

A、Partial thromboplastin time (PTT)
to 2 times the control.
B、Prothrombin time (PT)
to 2 times the control.
C、International normalized ratio (INR) of 3 to 4.
D、Hematocrit of 32%.