What role do the gland cells in Trichoplax adhaerens play? a) they secrete digestive enzymes
b) they help the animal move
O c) they are nerve cells
d) they make up the animal's ectoderm

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