What is the simple meaning of convection current?

Correct answer: Circular movement of material due to heat

The direct answer is A: circular movement of material due to heat. Convection current means that heat makes material move in a cycle. When a part of a fluid or semi-fluid material becomes hot, it generally becomes less dense and rises. Near the upper part it loses heat, becomes cooler and denser, and sinks. This rising and sinking can produce a repeated circular movement. Therefore, option A correctly describes both the cause, heat, and the movement, circulation. Option B is wrong because rainwater flow is surface water movement, not the general meaning of convection. Option C is wrong because dust settling in air is deposition, not a complete heat-driven circulation. Option D is wrong because a straight river current is caused mainly by slope and gravity, not by hot and cold parts rising and sinking. In geography, convection currents inside the mantle are used to explain movement of material and possible plate movement, although the mantle is solid but can flow very slowly over long periods. Memory cue: hot rises, cool sinks, and the cycle is convection.