Which of the following observations indica

问题：

Which of the following observations indicates that the mother of a child receiving home intravenous ampicillin therapy requires further teaching

A．The mother allows the antibiotic to run into the child's vein over a period of 30 minutes.

B．The mother flushes the venous access site with heparin 20 minutes after giving the antibiotic.

C．The mother stops the infusion when the area around the insertion site becomes hard and reddened.

D．The mother calls the home care nurse because the antibiotic solution will not infuse.