Identify a relic boundary other than the Berlin wall

What are the answers for the following questions?

You have been tasked with sorting the rock samples shown into three categories, with two rocks in each category. what attribute would you use to sort these rocks? which rocks would be in each category? rocks: obsidian, coquina limestone, granite, soapstone,pumice, and gneiss.

Iceland has taken advantage of its geology to meet a. political needs b. energy needs c. cultural needs d. economic needs answer b. energy needs