The correct answer is: C. Humayun.
Purana Qila, also known as the Old Fort, is a 16th-century citadel in the heart of Delhi, India. It was originally built by the Tomar Rajputs in the 11th century, and later rebuilt by the Mughal emperor Humayun in the 16th century. The fort is a UNESCO World Heritage Site.
Akbar was the third Mughal emperor, who ruled from 1556 to 1605. He was the son of Humayun and Hamida Banu Begum. Akbar was a great military leader and statesman, and he expanded the Mughal Empire to its greatest extent. He was also a patron of the arts and sciences, and he founded the city of Fatehpur Sikri.
Sher Shah Suri was the founder of the Sur Empire, which ruled over northern India from 1540 to 1556. He was a Pashtun warrior who defeated the Mughal emperor Humayun and captured Delhi in 1540. Sher Shah Suri was a great administrator and builder, and he is credited with building the Grand Trunk Road, which is one of the longest highways in the world.
Shah Jahan was the fifth Mughal emperor, who ruled from 1628 to 1658. He was the son of Jahangir and Mumtaz Mahal. Shah Jahan is best known for building the Taj Mahal, which is a UNESCO World Heritage Site. He also built the Red Fort in Delhi, and the Jama Masjid in Agra.
In conclusion, the correct answer to the question “Purana Qila at Delhi was built by” is C. Humayun.