have both of them be right next to each other at the same time and ask them what's going on so they can't lie while being right next to each other. If they both don't fess up just make sure they're always seperated.
I believe it's the Himalayan Mountain Range
Answer:
neolithic human population following the development of agriculture has been assumed to result from improvements in health and nutrition
597 billion in USD ranked first in 2015
