For energy resources, Poland's most important one is coal (and also lignite) which is mined in Upper Silesia in some large open pits mined there since the 19th century at least. It does have some petroleum in the Baltic Sea but still must import it from Russia.
C. The inner core is known to be made mostly of nickel and iron. However, since there is an outer core (which is the original one that's made out of nickel and iron), your answer might be D. But if you put it the 'core' in general, the right answer should be C.
I think the correct answer from the choices listed above is option D. Mineral deposits underground, farm products and lumber from forests are resources <span>of production called "natural resources" since they came from or produced in nature. Hope this answers the question.</span>
