This is the geologic theory where the cooler surface of the earth move slowly over the hotter layer underneath.

Explanation:

The Plate Tectonic Theory basically explains the major attributes of the geological phenomenon across the earth such as volcanoes,earthquakes,mountain and plateau formations by emphasizing on the movements of various continental plates located on the earth's surface.According to the theory,the upper crust or layer of the earth is known as Lithosphere which is further broken into various medium sized continental plates in various location across the earth.The lithosphere is positioned above a thick and moldable or permeable layer called Asthenosphere. Now, the continental plates constituting the lithosphere move constantly against or over one another causing various tectonic activities across the earth such as earthquakes,volcanoes,new geological formations and so forth. In this context,the cooler plates located on the top part of the lithosphere moves over the relatively hotter crust or layer located underneath causing tectonic plate movements and contributing to the various geological changes and occurrences.

answer; (b); i believe its indefinite existence of human population in a healthy and prosperous condition;