Which is the oldest mountain of the South America continent?

Explanation

The physiography of South America is mainly divided into three parts: the Andes Mountains in the west, a vast lowland in the middle, and the Guiana Highlands and the Brazilian Highlands in the east. These eastern highlands are considered the oldest landmass of the South American continent. Within these eastern highlands, there are two large ancient shield regions: the Guiana Shield and the Brazil/Amazonian Craton. The Guiana Shield is counted among the oldest geological formations on Earth. Among the given options, the Pacaraima Mountains are a part of the Guiana Shield. Therefore, the correct answer will be option (a).