What? What ancient people, where?

Across ? If they did not go across they would have merely returned or fallen off the side ?

Seriously, we don't do your homework here,
1. first because you need to study and learn the matterial
2. it is against the rules
3. what we may tell you from perhaps a senior level college course may not be the same as a freshman high school course. Even the text book you use may vary from some others in specifics. So you need to use YOUR books, to study YOUR work