Question

1. why is earths inner core solid?

earths inner core is a solid because the elements that make it up are only found as solids.
earths inner core is a solid because it is at a very high temperature.
earths inner core is solid because it is at a low temperature.
earths inner core is solid because of the pressure from the layers above it.

Explanation:

The inner core is composed of iron-nickel, which would be liquid at its extreme temperature, but the immense pressure from the overlying outer core, mantle, and crust compresses the material into a solid state. The other options are incorrect: the elements exist in other states elsewhere, high temperature would favor liquid, and the inner core has extremely high (not low) temperature.

Answer:

Earth's inner core is solid because of the pressure from the layers above it.