The correct answer is D. The Bering Land Bridge connects what is now Alaska to modern day northeast Asia. It would have allowed people to cross over into what we know as North America. Option A is incorrect, because humans would have to get to North America first before being able to spread throughout it. Option B is incorrect, because moving from South America to Canada would be moving north, not south. Option C is incorrect, because ships did not exist at the time of human migration out of Africa.