Answer:
Although the inner core is very hot, it is solid because it is experiencing very high pressure.
The outer core is not under enough pressure to be solid, so it is liquid even though it has a composition similar to the inner core.
Explanation:
The state of matter (solid, liquid or gas) of a given material depends on its temperature and pressure.
I believe that the three levels are:
1) primary or extractive: getting the resources. this includes for example producing milk (milking cows)
2) secondary: manufacturing: packaging the milk and treating it
3) tertiary: providing a service, for example bringing the milk to people's home!
I would either answer sanitation(pollution) or corruption
