What is an example of complexity in the natural world?

When coal has reached it hardest, darkest form, it is called select one: 0 a. sub-bituminous b. lignite c. bituminous d. antrhacite next page

Ialready know the answers to these questions and they are on the attachment. but i just need to know why that answer is the correct one. plz asap! this is for a report that i need to email by 10!

Which of these correctly describes the difference between processes that take place in prokaryotic and eukaryotic cells?