How did layers b and d compare in age if rock layers between b and d have eroded away what is the boundary between b and d called

Rock layer D is older than rock layer B. The boundary between both layers is called an unconformity.

Sorry if I happened to spell something wrong!

answer; natural resources;

metals are good conductor of electricity. it has free electrons on their surface. according to electron pool theory, each atom present in a metal crystal losses all of its valence electron and as a result a pool of free is form. these pool of electrons are free to move and   conduct electricity easily   while making metal as good conductor.

the correct answer is a. the ability of electrons to flow throughout the metal.

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