Question

1. which of the following describes what earths core is made up of and why it has that composition?

earths core is made of iron and nickel because they are the least dense elements that make up the earth.
earths core is made of iron and silicon because they are the least dense elements that make up the earth.
earths core is made of iron and nickel because they are the densest elements that make up the earth.
earths core is made of oxygen and silicon because they are the densest elements that make up the earth.

Explanation:

Earth's core is composed of iron and nickel. During the planet's formation, denser elements sank to the center due to gravity. Iron and nickel are among the densest elements in the Earth's composition. Options with silicon (less dense than iron/nickel) or oxygen (gas at core - relevant temperatures/pressures, not a major core component) are incorrect. Also, the core has dense elements, not the least - dense ones.

Answer:

Earth's core is made of iron and nickel because they are the densest elements that make up the Earth.