Which of the following statements about the civilizations in the americas is true? a. they traded actively with the mediterranean world. b. they were among the earliest christian civilizations. c. they developed in almost total isolation from the rest of the world d. they were invaded by nomadic tribes along their northern border.

The correct answer should be
c. They developed in almost total isolation from the rest of the world

Only in the new century was it made possible to discover them when shipping became developed enough to allow people to cross into the new continent. They developed isolated from everyone and only ever met other American tribes from time to time.