How to find the central idea when their is a lot of ideas in a text and how can i write a central idea?

Compare: what are the similarities and differences between "artificial flavors" and "natural flavors"? why does schlosser explain these two terms in such detail?

Fortify is a verb that means “to protect and strengthen.” a fortifications is a that means something that protects.

Which component is necessary to create an effective and debatable thesis statement