Correct Answer:
A. Karachi
Karachi is widely recognized as the Gateway City of Pakistan. This designation stems from its strategic coastal location and the presence of the Port of Karachi, which is Pakistan's largest and busiest seaport. It serves as a crucial entry point for international trade and commerce, making it the economic and maritime hub of the country. Peshawar is historically significant, known for the Khyber Pass. Lahore is the cultural capital, often called the 'City of Gardens'. Islamabad is the modern capital city, known for its planned infrastructure, but none of these serve as the primary maritime gateway like Karachi.