D. Obviously because it was large and they didn't have a lot of supplies to go across also it was very deep.
They weren't as accurate as they could be, in fact some were just based off of educated guesses.
Answer:
Asia and North-America
Explanation:
The Bering strait is a portion of about 47 miles (75 km) that separates Asia (Russia) and North-America (state of Alaska, USA). Let's remember that Alaska belonged to Russia and was bought by the US.
That straight is a place with very harsh and extremely violent weather fueled by cold Arctic water and winds.
20,000 years ago, that straight was solid ice and that's how human migrated from Asia to North America (and went further South afterwards).
since is says plural promise(s) i pick b. all of the above. because you cant just pick one its clever word play