With reference to the Himalayan rivers joining the Ganga downstream of Prayagraj from West to East, which one of the following sequences is correct?

Answer: (b) Gomati – Ghaghara – Gandak – Kosi

Gomati (near Ghazipur) → Ghaghara (near Chhapra) → Gandak (Patna–Hajipur) → Kosi (near Kursela).

The idea

Order tributaries by their confluences, the places where they join the main river. A tributary may rise far north or loop across the plain before meeting the Ganga. Its source, length and volume do not decide the west-to-east order of these meeting points.

Ganga below Prayagraj → Gomati confluence near Ghazipur → Ghaghara confluence near Chhapra → Gandak confluence near Hajipur → Kosi confluence near Kursela

Why the others are wrong

(a) The first two are swapped — the Gomati joins before the Ghaghara.

(c) Gomati and Ghaghara swapped, and the Kosi put before the Gandak.

(d) The Kosi is the LAST big left-bank river, at Bihar’s eastern end.

The trap

The Ghaghara is the biggest by volume, so people put it first. The order is set by WHERE each joins, and the Gomati joins first.

Elimination technique

Fix two anchors: Gomati joins before Ghaghara, and Gandak before Kosi. The first removes (a) and (c); the second removes (d).

Also know

The Yamuna meets the Ganga at Prayagraj, upstream of this sequence. The Son approaches from the plateau to the south and joins near Patna. Gomati, also written Gomti, rises in the Uttar Pradesh plain; grouping it with northern tributaries does not make its source a Himalayan glacier.