What does the evidence from multiple disciplines suggest is true about the first Native Americans?

a. The Americas were first populated by no more than 2-3 groups who migrated to the Americas at around the same time.
b. The Americas were first populated by diverse groups, but these groups share the same point of origin.
c. The Americas were first populated by groups who migrated from Asia to North and South America over the course of 500 years .
d. The Americas were first populated by widely diverse groups over the course of thousands of years