The confirmation of a strait between Asia and North America fueled an interest in the possibility of a wide plain that might have connected the two continents. Beginning in the early 1800s, American scientists and naturalists started investigating archaeological sites on the coasts of the United States. Their findings suggested that the first people to live in North America had come to the continent from another place. But where? It wasn't until the mid-1920s that scientists would finally restart the search for evidence of how people came to North America.

How is the CENTRAL idea developed in this section?
A: by illustrating the importance of archaeological sites farther south than expected
B: by describing the evidence that has been given to support the Bering Land Bridge theory
C: by emphasizing the idea that the first Americans have been studied for many years
D: by outlining the investigations and questions that led to the Bering Land Bridge theory