Question

as you read, jot down notes and drawings that will help you remember the meanings of these words. you can type or use the sketch/scribble button on the toolbar.
inner core
seismic waves
read it!
what is inside our earth?
the innermost layer of earth is the solid inner core. the inner core is also mostly nickel and iron, but it is solid because of extreme heat and pressure. the inner core is about 1,200 kilometers (750 miles) thick and is the center of our planet. humans have only been able to dig about 12 kilometers (7.5 miles) into the crust.
so, how do we know what else is down there? scientists use seismic waves to find out. when an earthquake or large volcanic eruption happens, it sends out seismic waves that travel through earth. scientists can track these waves as they move differently through solids and liquids. this helps us understand the layers of our planet without having to dig down to see them!

Explanation:

Since the problem isn't clearly stated (like defining a term, answering a question about Earth's layers, etc.), I'll assume a common question like "Define inner core based on the text" or "How do scientists study Earth's interior?". Let's take defining "inner core":

The text says the innermost Earth layer is the solid inner core, mostly nickel/iron, solid due to extreme heat/pressure, ~1,200 km (750 miles) thick, center of the planet.

Answer:

The inner core is the innermost, solid layer of Earth, mostly composed of nickel and iron, solid due to extreme heat and pressure, about 1,200 kilometers (750 miles) thick, and is the center of the planet.