Final answer:
The Americas were populated by Asian migrants 20,000-14,000 years ago through the Bering Land Bridge and coastal migration theories. Option A.
Step-by-step explanation:
The scientific theories of human origin in the Americas primarily focus on two key migration theories: the Bering Land Bridge and the coastal migration.
1. The Bering Land Bridge theory suggests that humans migrated from Siberia to Alaska during the last ice age, crossing over the land bridge that connected the two continents.
2. The coastal migration theory proposes that humans migrated along the coastal regions of Asia and eventually reached the Americas.
Both theories support the idea that the first inhabitants of the Americas came from Asia. Genetic sequencing shows that the earliest humans arrived in the Americas around 20,000-14,000 years ago, which makes the Americas the most recent continental habitation, excluding Antarctica.
So option A is correct answer.