George Clooney and Elisabetta Canalis asked to testify in Berlusconi trial

The video features a brief interaction with a greeting and a short response.

What does the phrase 'How are you?' typically signify in a conversation?

In what contexts might someone respond with 'No' after being asked 'How are you?'

How can the response 'No' affect the flow of a conversation?

What emotions or feelings might be conveyed by the response 'No'?

How important is it to understand non-verbal cues when someone responds with 'No'?