Final answer:
Shah Jahan planned to build a black marble mausoleum for himself opposite the white marble Taj Mahal, but it was never realized.
Step-by-step explanation:
It is said that Shah Jahan intended to build a black marble mausoleum for himself across from the white marble one, which is option a) The Taj Mahal. The Taj Mahal is a breathtaking monument in Agra, India, commissioned by Shah Jahan as a tomb for his favorite wife, Mumtaz Mahal. This architectural marvel reflects a blend of Indian, Islamic, Persian, and Ottoman influences. Despite plans for a matching mausoleum for himself, Shah Jahan was laid to rest beside his wife in the Taj Mahal, and the envisioned black marble counterpart was never constructed.