Another name for unicellular organisms that dominated earth up to the precambrian time is
a. eukaryotes.
b. cyanobacteria.
c. stromatolites
d. prokaryotes.

The other name  for unicellular organisms that dominated Earth up to the Precambrian time is called D. prokaryotes. Eukaryotes are different from prokaryotes such that prokaryotes are unicellular while eukaryotes are multicellular

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

The open ocean begins at the low-tide mark and extends to the end of the continental shelf

above statement is not a true statement about the open ocean because the open ocean has low levels of nutrients. most of the photosynthetic activity on earth occurs in the open ocean within the photic zone. organisms in the deep ocean are exposed to frigid temperatures and total darkness but it does not begin at the low-tide mark.