Final answer:
The root operation applicable when cautery is used to control postoperative hemorrhage is Control.
Step-by-step explanation:
The root operation that is applicable when cautery is used to control postoperative hemorrhage is Control. Cautery is a surgical technique that uses heat or chemical substances to burn or destroy tissue, including blood vessels, in order to stop bleeding. This technique is often used to control bleeding during and after surgery. Therefore, the appropriate root operation in this case would be Control.