A nurse is caring for a 1-year-old child who has been hospitalized. Which of the following items in the child's room is a common source of health care-associated infection?

The correct answer is D: Bedside computer keyboard. This is a common source of healthcare-associated infections due to frequent touching by multiple individuals without proper disinfection. Keyboards can harbor harmful bacteria and viruses, increasing the risk of transmission to patients. Disposable diapers (A) pose a low infection risk if disposed of properly. Protective gowns (B) are used to prevent contamination and do not typically harbor pathogens. Unopened formula bottles (C) are sterile until opened, thus not a significant infection source. In summary, the bedside computer keyboard is the correct answer as it can serve as a reservoir for pathogens due to frequent use without proper cleaning.