Question 1 of 36
How Borders Are Drawn
(1) A border is a line that marks where one country, state, or region ends and another begins. Some borders follow natural features, such as rivers, mountain ranges, lakes, or deserts. These are called natural, or physical, borders. For example, part of the border between the United States and Mexico follows the Rio Grande, and the Pyrenees Mountains separate France and Spain.
(2) Other borders are political borders that people agree on, often after a war or in a treaty, even where no physical feature exists. Some of these are geometric borders: straight lines that often follow a line of latitude or longitude. Much of the border between the United States and Canada follows the 49th parallel, the line of latitude 49° north.
(3) Natural borders are easy to see and can be easier to defend, but rivers can change course and mountains can be hard to divide exactly. Geometric borders are simple to draw on a map, but they often ignore the land and the people. A straight line can cut through a farm, a town, or a group of people who share a language and culture.
According to paragraph 1, which is an example of a natural border?
Hint
A natural border follows something in nature, such as a river or mountains.
Step-by-step solution
Paragraph 1 defines natural (physical) borders as borders that "follow natural features, such as rivers, mountain ranges, lakes, or deserts." It then gives an example: "part of the border between the United States and Mexico follows the Rio Grande."
Reasoning: the Rio Grande is a river, so a border that follows it is a natural border.
The correct answer is B.
Why not the others?
- A: the 49th parallel is a line of latitude. Paragraph 2 calls this kind of straight line a geometric border.
- C: a straight line along a line of longitude is also geometric, not natural.
- D: a line agreed on in a treaty where "no physical feature exists" is a political border (paragraph 2).
Tip: ask "Could I see this border from an airplane without a map?" Rivers and mountain ridges are visible, so they are natural. Lines of latitude and longitude exist only on maps, so they are geometric.