What was the greatest migration of the 20th century

What does this quotation from the introduction of thedeclaration of independence do?

This is the mountain range known as the alps. which of these statements regarding the alps is true? a) the alps are the largest mountain range in asia. b) the alps protect the roman empire from invasion. c) the alps were key in preventing england from being conquered in warfare. d) the alps prevented the roman empire from taking control of most of europe.

What period of history refers to the time when people did not have written records