Answer (a) — incorrect: While it is possible that those who took care of the index patient at the Star Hospital got infected by touching the patient, it fails to explain why 20 additional medical personnel got sick.

Answer (b) — incorrect: The index case was hospitalized in the regular inpatient ward. If the disease were air-borne, it would have quickly spread around the hospital through the building's common airshafts.

Answer (c) — correct: All cases occurred close in time--shortly after admission of the index case.This suggests that the source of infection was the same for all individuals at Star hospital. Further, the statements given by the Star Hospital cases suggests that they were in close physical contact with the initial case while visiting the index case. This suggests that the transmission occurred via direct contact with contaminated water droplets emanating from the sick case's sneezing or coughing.