Idk sorry if I knew I would help :(
A valley ca be formed by flowing water from a river.
This is true.
The definition of megalopolis is that it is a large urban area, huge and densely populated. St. Petersburg is definitely one, however, Miami is relatively small compared to other megalopolises so it might not fall within that category.
Answer:
Io, Europa, Ganymede, and Callisto.
