The pressure at the core is very high. The metals in the core are very heavy. The temperature of the core is very low. The chemicals in the core are very reactive.
I gave my students this multiple choice question: Which of the following most likely causes Earth's inner core to be a solid?

Only one answer is correct among these 4 choices:
- The pressure at the core is very high.
- The metals in the core are very heavy.
- The temperature of the core is very low.
- The chemicals in the core are very reactive.

Could you tell me which one is correct?

The pressure at the core is very high.