Why does hot material rise in the convectional current theory?

Correct answer: Because heating reduces its density

Direct answer: Option D is correct. Convection is movement caused by differences in temperature and density. When material is heated, its particles generally spread farther apart, so its density decreases. Less-dense hot material rises through denser surrounding material. Higher up, it loses heat, becomes denser and sinks. This upward and downward movement forms a convection current. Option A is wrong because heating normally decreases density rather than increasing it. Option B is wrong because cooling makes material heavier or denser, causing it to sink, not rise. Option C is wrong because seawater is not the basic reason hot material rises in the theory; the essential cause is the density difference produced by heating and cooling. Option D correctly states the direct cause: heating reduces density. In Earth science, convection in the mantle is a model used to explain movement related to plate tectonics, though the material is solid rock that can flow very slowly. Memory cue: hot and light rises; cool and dense sinks.