Answer the following question given this paragraph: 

The dense, iron core forms the center of the Earth. Scientists know that the core is metal from studying metallic meteorites and the Earth’s density. Seismic waves show that the outer core is liquid, while the inner core is solid. Movement within Earth's outer liquid iron core creates Earth’s magnetic field. These convection currents form in the outer core because the base of the outer core is heated by the even hotter inner core.


Q: Seismic waves show that the inner core of the earth is solid while the outer core is what?

 Choices:

- gas

- lava

- silicon

- liquid

A:
liquid
