The ‘Curzon Line’ is the boundary between:

The correct option is Poland and Russia.

Detailed Explanation:

The Curzon Line is a demarcation line proposed in 1919 by George Curzon, the British Foreign Secretary, as a potential armistice border between Poland and Soviet Russia during the Polish-Soviet War (1919–1921).

Although it was not accepted at the time, the Curzon Line became significant following World War II when it was used as the primary basis for establishing the official eastern border of Poland with the Soviet Union (presently bordering Poland with Russia, Belarus, and Ukraine).

Let us briefly review the other options for clarity:

• India and Pakistan: Separated by the Radcliffe Line and the Line of Control (LoC).
• North and South Korea: Separated by the 38th Parallel and the Military Demarcation Line (MDL).
• USA and Canada: Largely demarcated by the 49th Parallel north.

Therefore, the Curzon Line is the boundary associated with Poland and Russia.