Each dimension and metric has a scope that aligns with a level of the analytics data hierarchy — user, session, or hit-level. In most cases, it only makes sense to combine dimensions and metrics in your reports that belong to the same scope. Which of the following is a valid dimension / metric combination?

Session (metric) + Page (dimension)
Bounce rate (metric) / Event Action (dimension)
Sessions (metric) / city (dimension)
All of the above are valid dimension / metric combination