Head nods, murmurings, facial expressions, and eye contact from audience members are all forms of

Feedback.

Explanation:

Feedback is an output information of the performance of anything.

The gestures given in the question are examples of non-verbal communication. Non-verbal communication is communication that is not communicated through mouth or by words but by body language or gestures.

The given list in question are all forms of feedback from the audience. When an audience listens to the speaker they give non-verbal feedback by making eye contact, nodding their heads on the points they agree with, even facial expressions of the audience is a form of feedback.

So, all elements of the list in the question are a form of feedback.