- The inner core is located in the center of the earth
- The pressure at the center of the earth is extremely high
- So, the inner core of the earth is under extremely high pressure

- The inner core of the earth is under extremely high pressure
- Extreme high pressure causes the inner core of earth to be in solid state
- Hence, the inner core of earth is solid

Therefore, the inner core of earth is solid
Q: Which property of Earth's interior keeps the innermost part in a solid state?
Context:
- The inner core is located in the center of the earth 
- The pressure at the center of the earth is extremely high 
- Extreme high pressure causes the inner core of earth to be in solid state