Which of the Following Best Explains the Relative Lack of Communication

Which of the following best explains the relative lack of communication between the people of the Americas and Afro-Eurasia after about 6,000 BCE?

A) A new Ice Age created massive impassable glaciers separating the Americas from Afro-Eurasia.
B) Melting glaciers covered the land bridge between East Asia and the Americas with water,physically separating the continents.
C) The peoples of these two regions pursued fundamentally different strategies for finding food,so they had little desire for communication.
D) The peoples of Afro-Eurasia refused to adapt to changing environments.