Which would be considered the most sincere method of communication when offering support to a friend who is depressed about a recent break-up?

A: Facebook post
B: Text message
C: Email
D: Phone call

D: Phone call

A phone call allows for more direct and personal communication, giving the friend the opportunity to hear the sincerity and empathy in the supporter's voice. It also allows for a more immediate and real-time response, showing the friend that they are valued and cared for.