In what situation must actors focus on the communicative power of slight facial gestures while ignoring the expressive potential of their bodies?

The correct answer is - filmed in a close up.

Explanation:

Close up in camera view or in the film making, is a type of the camera shot that involves the facial expression of the actor rather than the expressions that involved the physical expressive potential of the body.

In this shots facial gestures are include the expression and di·a·logue that express the feelings of the character they play.

Thus, the correct answer is - filmed in a close up.