The longest border between any two countries in the world is between :

Correct Option (A)

The border betweenCanadaand theUnited States of Americais thelongest international borderin the world shared by any two countries. Its total length is approximately8,890kilometres (5,525miles).

• This extensive border includes both a land boundary across various U.S. states and Canadian provinces, and maritime boundaries in the Great Lakes as well as along the Atlantic and Pacific coasts.
• It is largely characterized by peaceful demarcation, established through bilateral treaties and natural geographical features such as rivers and mountain ranges.

Incorrect Options

(B) Chile and Argentina: This option is incorrect. The shared border between Chile and Argentina is approximately 5,308 km long, making it the third-longest international land boundary globally, not the longest overall.

(C) China and India: This option is incorrect. India shares an approximate border of 3,488 km with China. This length is significantly shorter than the Canada-United States border.

(D) Kazakhstan and Russian Federation: This option is incorrect. The border between Kazakhstan and the Russian Federation measures approximately 6,846 km. This makes it the second-longest international land border in the world, but not the longest overall.