Which of the following instructions is crucial for the nurse to give to both family members and the patient who is about to be started on a patientcontrolled analgesia (PCA) of morphine? ( )

A、Onlythepatientshouldpushthebutton.
B、DonotusethePCAuntilthepainissevere.
C、ThePCAsystemcansetlimitstopreventoverdosesfromoccurring.
D、Notifythenursewhenthebuttonispushed.
E、Donotpushthebuttontogotosleep.