B.
All dentist equipment is used in the mouth. Many deseases, bacteria and viruses are transmitted trough saliva, and not all of these are weak. So, that is why we clean the dental operatory, to lower the chances of transmitting anything.
Hope it helped,
BioTeacher101
Through the action of force. Gravitational force- when gravity accelerates a falling object, it converted its potential energy to Kinect energy