The correct answer is option 2, Ustad-Isa.
Option 1, Mohammad Hussain, is not a correct answer. The architect of the Taj Mahal was not Mohammad Hussain.
Option 3, Shah Abbas, is also not a correct answer. Shah Abbas was the name of a ruler of the Safavid dynasty in Iran, and he is not associated with the Taj Mahal in any way.
Option 4, Ismail, is not a correct answer either. There is no known architect by the name of Ismail who is associated with the Taj Mahal.
Therefore, the correct answer is Ustad-Isa, who is known as the architect of the Taj Mahal.