The Durand Agreement of 1893 was a significant agreement that demarcated the Indo-Afghan border. This agreement was signed between Sir Mortimer Durand, representing British India, and Amir Abdur Rahman Khan of Afghanistan.

Option 1: Indo-Afghan border. This is the correct answer. The Durand Agreement established the border between British India (now Pakistan) and Afghanistan. The agreement defined a border line known as the Durand Line, which stretched for approximately 2,200 kilometers and separated the two countries.

Option 2: Indo-Tibetan border. This is not the correct answer. The Durand Agreement did not involve Tibet in any way. It focused solely on the border between British India and Afghanistan.

Option 3: Indo-Nepal border. This is not the correct answer. The Durand Agreement did not pertain to the border between British India and Nepal. This agreement specifically dealt with the Indo-Afghan border.

Option 4: Indo-Sikkim border. This is not the correct answer. The Durand Agreement did not address the border between British India and Sikkim. It was solely concerned with demarcating the Indo-Afghan border.

In conclusion, the Durand Agreement of