The correct answer is (d).
The Heart of Asia Conference is an annual multilateral meeting of foreign ministers from Afghanistan, Azerbaijan, China, India, Iran, Kazakhstan, Kyrgyzstan, Pakistan, Russia, Saudi Arabia, Tajikistan, Turkmenistan, Uzbekistan, the United States, and the European Union. The conference was established in 2011 to promote regional cooperation and stability in Afghanistan.
In 2015, the Heart of Asia Conference was held in Islamabad, Pakistan. Foreign Minister Sushma Swaraj attended the conference as part of a larger diplomatic effort to improve relations between India and Pakistan.
The other options are incorrect because they are not cities in Pakistan. Karachi is the largest city in Pakistan, but it is not the capital. Peshawar is a city in the Khyber Pakhtunkhwa province of Pakistan. Lahore is the second largest city in Pakistan and the capital of the Punjab province.