No matter how much work you put into your research and thesis, or how much time you spend on viva prep, there’s always something that your examiners could say or ask that you haven’t anticipated.
And no matter what they ask, because of all of the work you’ve committed to your research and thesis, and all the time you’ve invested into getting ready, there’s always something you can do to respond to their questions and be part of the discussion.
You can ask a question. You can pause. You can think. You can check your thesis. You can remember something. You can take a situation and analyse it. You can work through a question or a problem. You can, in the end, always find a way to respond.
Whatever situation you find in the viva, there’s always something you can do.