The east coast of present-day north america is a good example of a(n) continental margin.

The correct answer is - Passive.

The passive continental margins are transitional zones between the oceanic and continental crust, lithosphere, and it is not an active plate margin. This type of margins form from sedimentation over an ancient rift, which has now become a transitional lithosphere. This type of margins can be found further away from the ocean ridges, but also away from the active continental margins. The east coast of North America is a nice example of a passive continental margin. It has all the characteristics of it. It is made out of sediments, it is a transitional zone between continental and oceanic lithosphere, it is far away from the mid-ocean ridge from one side, and the active continental margins on the other side.