Detailed Solution:
The correct answer is “India and China”.
The McMahon Line is a boundary line between India and Tibet (which is now a part of China), named after Sir Henry McMahon, the foreign secretary of British India who drew the line in 1914.
The McMahon Line was intended to delineate the boundary between British India and Tibet, which was then under Chinese control. The line was drawn after negotiations between the British government and Tibetan representatives, and was subsequently agreed to by the Chinese government.
After India gained independence from Britain in 1947, the McMahon Line became the de facto border between India and China.