Which of the six essential elements of geography helps us better understand physical and cultural similarities and differences around the world? A. movement B. the world in spatial terms C. human-environment interaction D. places and regions

This is a 2017 topographic map of puerto rico in the united states, and i'm sorry that people there have suffered such a disaster. i want to ask, what do the yellow dots and areas represent on this graph? and the blue area and the little blue circle, and the little blue sign that looks like a signal tower, what do they stand for?