Which statement correctly describes convection current?

Correct answer: Hot material rises and cool material sinks

Convection is a circular movement produced by differences in temperature and density. When a material is heated, it usually expands, becomes less dense, and rises. As it moves away from the heat source, it cools, becomes denser, and sinks. This rising and sinking can continue as a cycle. In discussions of Earth’s interior, the idea is used to describe how heat movement in the mantle may contribute to large-scale geological motion.

Option A is correct because it states the basic rule: hot material rises and cool material sinks. Option B denies movement and therefore contradicts convection. Option C limits the process to river water, although convection can occur in fluids and, under suitable conditions, in slowly moving mantle material. Option D does not describe convection at all. Remembering the linked ideas of heat, density, rising, sinking, and circulation leads to the correct choice.