Final answer:
The nurse should instruct the practical nurse (PN) to avoid urinary catheterization and encourage the client to urinate naturally to help flush out bacteria.
Step-by-step explanation:
The nurse should instruct the practical nurse (PN) to avoid urinary catheterization when caring for a client with prostatitis. Prostatitis is inflammation of the prostate gland, and using a urinary catheter can introduce bacteria into the urinary tract, potentially worsening the infection. Instead, the client should be encouraged to urinate naturally to help flush out bacteria. If necessary, a urine sample can be collected by having the client strain their urine (option c).