Why do scientists think earths core contains iron?

A iron is lighter than silicon

B iron is a heavy element and would sink into the planet

C the crust also contains a great deal of iron

D iron does not conduct electricity

The best answer seems to be B. iron is a heavy element and would sink into the planet because iron is a metal so it is heavy and when something is heavy it sinks the lowest it can go, so when the earth was developing, iron and other heavier substance sunk towards the middle of earth