What is the basis for calling Earth's surface a dynamic system in later studies?

Correct answer: Plate movement seafloor spreading and active geological belts

The direct answer is A: plate movement, seafloor spreading, and active geological belts support the idea that Earth’s surface is dynamic. ‘Dynamic’ means changing or active rather than permanently still. Step by step: tectonic plates move; new crust forms at some mid-ocean ridges through seafloor spreading; old crust may sink at subduction zones; earthquakes, volcanoes, and mountain building occur in active belts; together these observations show continuing change in the lithosphere. Option A is correct because it combines several independent geological evidences. Option B is wrong because river names do not prove movement of Earth’s crust. Option C is wrong because the number of cities describes human settlement, not tectonic activity. Option D is wrong because crop distribution concerns agriculture and climate, not plate motion. Exam cue: dynamic Earth means plates, spreading, subduction, earthquakes, volcanoes, and mountains.