To find out what you need, you would have to see if it was factual.
If you find that out, you need the most information possible. If you dont have alot of information on any of them, choose the one with the most. In my opinion, it think it would be a .gov sight. Those types show what you need, and it is a governmant website. So you know that you need www.usgs.gov/edu/sinkholes
You are welcome.
