A Nurse Walks Up to a Computer in the Hallway

A nurse walks up to a computer in the hallway and presses the index finger to the sensor, thereby gaining access to patient data. A few moments later another nurse performs the same steps and is granted access. A visitor who is watching from a room walks over and places the index finger on the sensor, only to receive an "error and access denied" message. Security is being maintained by:

A) robot technology.
B) biometric technology.
C) telehealth.
D) ubiquitous computing.