The correct answer is - b. Precambrian.
The Canadian Shield, also referred to as the Laurentian Plateau, and Bouclier Canadien, is actually the basis around which the North American continent had formed as we now know it.
It is a very big area that is exposed and is composed out of Precambrian igneous rocks, as well as high-grade metamorphic rocks.
This area is actually the area that contains one of the oldest rocks on the whole planet, and it is an area that in the far geologic past was part of the super-continent Pangaea, and afterwards it was part of the Laurasia continent.
