scientists find dense rock on earths surface that is made of magnesium and smaller parts of alumminum and silicon. what layer of earth might help this rock help study? explain youre reasoning

Iwould say silver and gold

Are you asking about a street map usage  if so here is your answer  a street map for a very limited area could simply be a bit map or a .jpg image.  but a more general map would probably store the streets as vectors.  but you shouldn't assume that there is one way to do it

It has been around since 1858 so b. false