The border between Canada and the United States is a

It's an international border...

Explanation:

The border was an established agreement between the U.S. and Britain

The treaty between the U.S. and Britain, established the 49th parallel from the Rocky Mountains to the Strait of Georgia; this is the boundary between the U.S. and Canada.

This agreement took place in 1818.

tbh I'm kinda confused by what you're asking

I hope what I put answers your question tho

this null effect is caused by a weak manipulation and ineffective internal validity. in a scientific study, as the one dr. morimoto is trying to perfom, internal validity refers to the confidence placed in the cause-effect relationship and to how well an experiment is done and able to eliminate confounding variables.        

answer; /// the correct answer is (a) burned the city;