Which heavy materials are mainly found in Earth's core?

Correct answer: Iron and nickel

Direct answer: D, iron and nickel. Earth has layers because, when the young planet was very hot and partly molten, materials separated according to density. Dense materials moved downward toward the centre, while lighter rocky materials remained above. Earth’s core is therefore mainly metallic, with iron and nickel as its major components; the inner core is solid and the outer core is liquid because of different pressure and temperature conditions. Option A, sand and soil, are surface materials, not core metals. Option B, ice and water, are light surface or near-surface materials. Option C, wood and coal, are organic materials found near the crust and cannot form the metallic core. Option D is correct. Memory cue: heavy metal centre—iron and nickel.