Which of the following Mughal period canals was constructed by restoring the Rajabwah of Firuz Shah?

The correct answer is B) Shahab Nahr, also called Shah Nahr. Shah Jahan's engineers in Delhi re-excavated and restored the old Rajbaha (royal canal) that Firuz Shah Tughlaq had built, bringing Yamuna water into the Shahjahanabad area. The point to remember is that it was a restoration of an older Sultanate channel, not a wholly new Mughal cut.

• A) Shekhnu-Ni: Not the canal linked with Firuz Shah's Rajbaha restoration in standard sources.
• C) Nahr-i-Bihisht: Associated with the Mughal water-supply works of Shahjahanabad under Ali Mardan Khan, a separate project, not the Firuz Shah Rajbaha restoration.
• D) Nahr-i-Agra: Linked with the water supply of Agra, not with the Delhi Rajbaha.

The core concept is Mughal hydraulic engineering: the Mughals repaired and extended earlier canal networks rather than building only from scratch. This connects to the Art and Culture and Medieval History sections, and to a Mains angle on how urban water infrastructure supported imperial capitals.

Trap: Aspirants see "Nahr" in all the options and pick the one they recall most often. Anchor the answer to the specific link between the canal and Firuz Shah's Rajbaha, and verify that link against a reliable source before you commit.