Answer :
If the Earth's differentiation were any different, it may have affected its gravitational pull and tectonic activity.
The geological processes that resulted in change of interior structure of Earth is known as differentiation.
Tectonic Activity is the movement of tectonic plates in the earth crust which gives rise to the volcanic activities.
Therefore, tectonic activity such as volcanic activity are also essential to creating our atmosphere by participating in the various atmospheric cycles.
Hence, The correct answer is A.) Tectonic Activity
