Step 1: Understanding Mughal architecture.
The Mughals were known for their grand architecture, including structures like the Taj Mahal, Lal Qila, and Humayun's Tomb. However, the Qutub Minar was built by Qutb-ud-Din Aibak, the founder of the Delhi Sultanate, not by the Mughals.
Step 2: Analyzing the options.
(A) Taj Mahal: The Taj Mahal was built by Emperor Shah Jahan and is a famous example of Mughal architecture.
(B) Lal Qila: Lal Qila, or the Red Fort, was built by Shah Jahan and is another example of Mughal architecture.
(C) Qutub Minar: Correct. The Qutub Minar was built by Qutb-ud-Din Aibak and is not a Mughal structure.
(D) Humayun's Tomb: Humayun's Tomb was built by Humayun's wife, Empress Bega Begum, and is a famous Mughal tomb.
Step 3: Conclusion.
The correct answer is (C) Qutub Minar, as it was not built by the Mughals.