Why did iron and nickel become concentrated in the core of early Earth?

Correct answer: They were heavy metals and sank inward in the molten state

Direct answer: Option A, they were heavy metals and sank inward in the molten state. Early Earth became hot enough for much material to melt or soften. In that condition, gravity separated substances by density. Iron and nickel are much denser than the silicate rocks that form much of the mantle and crust, so they moved downward and collected at the centre. Lighter materials remained above and later formed the mantle and crust. Option A is correct because it gives both the cause—high density and gravity—and the process—sinking through molten material. Option B is wrong because iron and nickel are not the lightest gases; they are solid metallic elements. Option C is wrong because they are not light particles arriving directly from sunlight. Option D is wrong because they did not dissolve in water to form clouds; core formation occurred inside the hot young Earth. Exam cue: iron and nickel are heavy, so remember them in the core.