If an exam question says core is made only of silica and magnesium why is it wrong?

Correct answer: Silica and magnesium are associated with SIMA, whereas the core is mainly nickel and iron (NIFE)

Silica and magnesium are associated with SIMA, a term used for the Earth’s upper rocky layers. In contrast, the core is composed mainly of iron and nickel, called NIFE. Option D is also incorrect because the inner core is largely solid and the core contains nickel as well. Exam tip: Remember SIAL, SIMA and NIFE as composition-based terms for the Earth’s layers.