Which Statement Best Defines "Sight and Sound Supervision

Which statement best defines "sight and sound supervision?"

A) Teachers must be able to both see and hear children at all times.
B) Teachers must train children to look at and listen to their instructions at all times.
C) Children must be able to both see and hear the children at all times.
D) Children must be able to respond to "1-2-3,eyes and ears on me" spoken by the teacher.