Final answer:
The nurse should include the statement: "Let a staff member know if you experience any trouble breathing."
Step-by-step explanation:
When teaching a client about prescribing morphine via a patient-controlled device after a cesarean section, the nurse should include the statement: "Let a staff member know if you experience any trouble breathing." This is because morphine can cause respiratory depression as a side effect, and it is important to monitor for any difficulty in breathing. The other statements are not accurate or relevant to the medication administration.