I am sure if you had posted your comment on a US cities quiz you wouldnt have gotten any remarks along the lines you have now. (Maybe you meant only for the boston question, but since you talk about "all the complaints this quiz gets" it seems like you are implying an american source is needed for áll the questions. I think that is where people perhaps read it differently than you intended :) )
The largest city in New England, the city proper, covering 48 square miles (124 km2), had an estimated population of 636,000 in 2012, making it the 21st largest city in the United States. The city is the anchor of a substantially larger metropolitan area called Greater Boston, home to 4.5 million people and the tenth-largest metropolitan area in the country. Greater Boston as a commuting region is home to 7.6 million people, making it the sixth-largest Combined Statistical Area in the United States.
I have no clue what the quiz means to include within "urban area", but (maybe) one of these numbers would be it.
I know everybody can makes typos, so I am not serious about this (though who know maybe it is true..) But I couldn't let this one go, had to make the remark :)
So Boston is the center of a CSA that includes Manchester, Worcester, and Providence and their surrounding areas. All of these places clearly have social or economic linkages that are centered in Boston. This isn't hard.
Also- keep in mind that the geographic size of the Boston CSA is pretty close to, say, Dallas or St. Louis. Just because an area has lots of different subdivisions as a function of when it was founded doesn't mean it can't be a CSA.
Ok I forgot the rest of my comment, had started it on another day and apparently never finished it haha