Final answer:
The breakup of Pangaea led to the formation of rift valleys, which are the most visible products of continental rifting as two large landmasses began drifting apart.
Step-by-step explanation:
According to the Plate Tectonics theory, the most visible product after the first break of Pangaea into two large land masses was d. rift valleys. The theory of plate tectonics describes the movement and interaction of the Earth's lithosphere plates. When Pangaea started to split around 200 million years ago, it initiated a process known as continental rifting.
As South America and Africa started to separate, the rifting process was clearly recorded on the eastern Brazilian margin. This significant event in Earth's history resulted in the formation of rift valleys – depressions formed as the lithospheric plates moved apart. Over time, these valleys expanded and new oceanic crust formed between them. An example of a rift valley is the East African Rift Valley, which was formed due to the separation of the African and Arabian plates.