The stimulus that is needed for continued and sustained production of breast milk is

Infant suckling

Infant suckling is the stimulus that is needed for continued and sustained production of breast milk. When an infant suckles, stimuli are transmitted to the mother's pituitary gland and prolactin (a hormone responsible for milk production) is released by the pituitary and this leads to the production of more milk. The more an infant suckles, the higher the prolactin level and the amount of milk produced.

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

Your answer is going to be a. i know my biology