Which one of the following country shares the largest border with Pakistan?

Correct Answer: D. Afghanistan 

Afghanistan shares the largest border with Pakistan. The border between Pakistan and Afghanistan is 2611 kilometers long. The border between Pakistan and Afghanistan is called the Durand Line. The border came into existence in November 1893. The Pakistan-India border is almost 2,100 kilometers long.
Reference: http://www.surveyofpakistan.gov.pk/SiteImage/Downloads/pakistan_showing_border_length.pdf