In Convectional Current Theory density is related to what?

Correct answer: Temperature

The direct answer is D: in Convectional Current Theory, density is related to temperature. Density tells how much matter is packed into a given volume. When mantle material is heated, it expands; the same material occupies more space, so its density decreases and it tends to rise. When the material cools, it contracts; its density increases and it tends to sink. This difference in density creates a circulating movement called convection. Option D is correct because temperature changes produce changes in density that drive the current. Option A is wrong because a political boundary concerns administration, not physical movement inside Earth. Option B is wrong because river length does not explain mantle convection. Option C is wrong because plant colour has no role in this geological process. The important chain is heat change, density change, rising or sinking, and circulation. Memory cue: hot means lighter and rising; cool means denser and sinking.