Which Mughal monument is the first to be faced entirely in white marble and to use pietra dura inlay?

The correct answer is C, Tomb of Itmad-ud-Daulah. Nur Jahan built it at Agra between 1622 and 1628 for her father Mirza Ghiyas Beg, who held the title Itmad-ud-Daulah. It is the first Mughal building covered wholly in white marble and the first in which pietra dura, the inlay of cut coloured stones into marble, is used on a large scale. Its small size and delicate finish have earned it the nickname the Baby Taj, because it marks the change from the red sandstone of Akbar to the marble of Shah Jahan.

Option A, the Taj Mahal, carries pietra dura to its highest point but comes later, from 1632. Option B, the Moti Masjid in Agra Fort, is also in marble but belongs to Shah Jahan. Option D, the Buland Darwaza, is of red sandstone with only marble inlay and was built by Akbar in 1575, before the marble phase began.