The Mound Builders were generally known for "<span>d. building large cities," since they would build "mounds" that were used for a variety of purposes--religious, residential, etc. </span>
I would say the answer would be new technology.
Well it has to do with the way he said it
Answer:
This is a list of the European Union cities with the highest population density. The population ... The population density of the cities listed is based on the average number of people living per square mile or per square kilometer.Explanation:
