The breakup of Pangaea, which began around 175 million years ago during the Jurassic period, was primarily caused by the process of plate tectonics. Specifically, rifts developed between various landmasses as tectonic plates began to move apart due to underlying mantle convection, leading to seafloor spreading.
Of the options provided, the most accurate description is:
Rifts developed between the eastern United States and western Africa and between the other landmasses.
This reflects the idea that the continents were torn apart along rift zones, leading to the formation of new ocean basins as landmasses drifted to their current positions. The breakup also contributed to changes in climate and biodiversity due to the fragmentation of ecosystems.