North america- list and describe a specific example of an ocean or river and how it was a barrier and or roadway

North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere; it is also considered by some to be a northern subcontinent of the Americas

I  cant see the question.

The sun's parallax would be 180 degrees, greater than which you can't get.  so a. would be your anwser