Car manufacturers and plastic bottle making
I Don't see any multiple choice answers but i'm going to take a gander and guess that the answer you are looking for is "<u>Coal</u>"
If I'm not mistaken, it was used as a neutral zone. Basically splitting hostiles from non-hostiles. It was also being used as a safe haven for the poor who couldn't pay taxes.
I hope this is the answer you were looking for and that it helps!! :)
Mauna kea is technically the tallest.