Pennsylvania was known as the ? ? workshop of the world? because it was home to the world'? ? s largest industrial companies. a. true b. false

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?