Correct Answer:
A. Afghanistan
The correct answer is Afghanistan. When Pakistan applied for membership in the United Nations in 1947 after its independence, Afghanistan was the only country to vote against its admission. Afghanistan opposed Pakistan's membership due to the unresolved Durand Line border dispute and claimed the Pashtun territories. Among the options:
- Afghanistan: Correct; it cast the sole opposing vote.
- India: Did not oppose Pakistan's UN membership.
- Iran: Supported Pakistan's membership.
- United Kingdom: Supported Pakistan's membership.
Therefore, the country that opposed Pakistan's UN membership is "Afghanistan".