The physical regions marked as 1, 2, 3 and 4 on the given map are respectively

The western margin marked 1 is the Andes mountain chain, which runs along South America’s Pacific edge [1]. The area marked 2 corresponds to the Brazilian Shield or Brazilian Highlands, the old plateau region occupying much of eastern and central Brazil south of the Amazon [2]. Marking 3 fits the Guiana (Guyana) Highlands — the forested plateau between the Orinoco and Amazon rivers in southern Venezuela, Guyana and northern Brazil [2]. Finally, region 4 is the Amazon Basin, the extensive lowland drainage and tropical rainforest occupying central-northern South America [3]. These positions match option 1: Andes, Brazilian Shield, Guyana Highlands and Amazon Basin.

Sources

1. [1] https://www.nationsonline.org/oneworld/map/South-America-maps.htm
2. [2] https://education.nationalgeographic.org/resource/south-america-physical-geography/
3. [3] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 3: MAJOR BIOMES > 1. Tropical Evergreen Rainforest Biome > p. 5