What is the direct result of density change in Convectional Current Theory?

Correct answer: Rising or sinking of material

Direct answer: A, rising or sinking of material. Density means how much mass is packed into a given volume. In a heated convection system, material expands, so its density decreases and it tends to rise. As it cools, it contracts, its density increases, and it tends to sink under gravity. The exact chain is: temperature changes; volume and density change; buoyancy changes; material rises or sinks. Option A is correct because it directly describes the physical result of density variation in convection currents. Option B is wrong because a river changes course through erosion, deposition, floods or tectonic effects, not as the immediate result meant here. Option C is unrelated to mantle density and concerns urban growth. Option D is unrelated because rainfall stopping is a weather event, not the direct convection result. Memory cue: lower density floats upward; higher density moves downward. The supplied answer is consistent.