the correct answer would be earthquakes because it gives us the answer right in the question by saying "a region where tectonic activity is", and in earthquakes they call the parts of the earthquake where it moves the ground apart tectonic plates.
Hope I helped.
Tides would most likely be all over the place and unstable, and their wouldn't really be a full moon.
I am unsure of how to answer this completely, but I will give it my best.
It could be meant that there is no physical boundary holding them apart and that the world's oceans simply flow into each other rather than being separated. Such as the pacific and Atlantic. They are not held apart, they flow around countries and flow into each other at a certain point.
