Which Statement About the Use of Thermometers Is True

Which statement about the use of thermometers is true?

A) The use of external thermometers, such as the tympanic thermometer, poses less risk of infection for your patient.
B) You do not need to wash your hands after taking a patient's temperature with a forehead or skin thermometer because it is not an invasive procedure.
C) The rectal method is preferred over the tympanic method.
D) Tympanic thermometers can harbor an infectious biofilm that may not be visible.