What is the Earth's core?

• A. The Earth's mantle layer.
• B. The Earth's crust.
• C. The Earth's innermost layer.
• D. The Moon's core.

Answer: (C)

The concept being tested is where the Earth’s core is located and what it comprises. The core is the center part of the planet, lying beneath the mantle, and it is the innermost layer. It isn’t the crust or the mantle, and it isn’t related to the Moon. In fact, the core has two parts: an outer liquid layer made mainly of iron and nickel, and an inner solid sphere also mainly iron-nickel. The inner core remains solid because the pressures at Earth’s center are immense, while the outer core is liquid and flows, which helps generate Earth’s magnetic field. So the best description is that the core is the Earth's innermost layer.