The correct answer for who designed the Gol Gumbaz is option 4 - Yaqut of Dabul. Yaqut of Dabul was a renowned architect during the reign of King Ibrahim Adil Shah II in the 17th century. He was given the responsibility of designing and constructing the Gol Gumbaz in Bijapur, Karnataka, India.

Option 1, Ustad Ahmad of Lahouri, is not correct. Ustad Ahmad was the designer of the Taj Mahal in Agra, not Gol Gumbaz.

Option 2, George Wittet, is also not correct. George Wittet was an architect who designed several prominent buildings in Mumbai, such as the Gateway of India and the Prince of Wales Museum.

Option 3, Henry Irwin, is not correct either. Henry Irwin was an architect known for his work in British India, including the Bangalore Palace and Mysore Palace, but not the Gol Gumbaz.

Alert - correct answer should be Ustad Ahmad of Lahauri