Geojson and D3 map

Answer to Q1: The city located at -73.66333007812499, 45.4986468234261 is montreal

Answer to Q2: D3 knew to put the generated image into the right spot because the coordinates were given. Line 18 is the one that controls it

Answer to Q3: They chose to use a value of around 90 because thats where north and south america are

Answer to Q4: you use text decoration: underline in a comment