Final answer:
The nurse should enter number 4. 2300 to document a wound irrigation implemented at 9 p.m. in military time.
Step-by-step explanation:
The nurse should enter number 4. 2300 to document a wound irrigation implemented at 9 p.m. in military time. In military time, 9 p.m. is represented as 2100, but since the nurse is using the 24-hour clock, the number to be entered would be 2300.