Hey guys i just wanted to know if any of you knew what the use of knowing the freezing point of water could be

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

4, two dominant and two recessive

Yes yes yes very good