What is the oldest and most stable part of a continent? a craton b pluton c shield d crust

The correct answer is letter A.  

The Craton is the oldest and most stable part of a continent. It came from the Greek word “kratos” which means strength. It has survived many cycles of merging and rifting of continents and is now generally found within the interiors of the tectonic plate. They are composed of a basement rock that is made out of ancient crystalline which are possibly covered by younger sedimentary rock. 

It’s either c or d as the answer.