The correct response is:
Around that time, those regions were located in tropical climates that were partially submerged on the coasts.
This observation supports the theory of plate tectonics because it suggests that the continents were once arranged differently, allowing areas that are now coal-rich to have been located in suitable environments (tropical climates) for coal formation. This aligns with the movement of tectonic plates over geological time, altering the positions of landmasses and climate conditions.