Which statement best compares coal and ores?
both are burned for energy.
both take millions of years to form.
both require oxygen to form.
both are used to make coins.

I think the correct answer from the choices listed above is the second option The statement that best compares coal and ores would be that both take millions of years to form. They are  formed millions of years ago when the earth was covered with huge swampy forests where plants - giant ferns, reeds and mosses - grew. 

Variables,control,conclusion and finally scientific theory