Final answer:
To properly care for an infant with myelomeningocele, a nurse should cover the sac with a sterile, moist dressing and ensure protective positioning and monitoring for complications.
Step-by-step explanation:
The correct action for a nurse caring for a 2-day-old infant with a myelomeningocele is D. Cover the sac with a sterile, moist dressing. Myelomeningocele is a type of spina bifida where the spinal cord and the meninges protrude through an opening in the spine. Until surgery is performed, it's vital to protect the area from infection and to maintain the integrity of the tissues. The nurse should also ensure the infant is placed in a position that does not put pressure on the sac, typically the prone position, and keep a vigilant eye for any signs of infection or other complications.