This is about you looking ahead and working out what the safest thing to do is based on what you see happening. You are not expected to be an expert, but you are expected to be safe. Remember the criteria is safe with a bit of confidence. Confidence being made up of skill, judgement and experience.
You will have access to the same information as the examiner, as to what is happening on the road. So if something catches you by surprise hopefully it will also have surprised the examiner. The thing here is how you deal with it. This will mirror life on the road after you passed. Safe with a bit of confidence is what we aim for here.